lavc: add VideoToolbox H.264 Encoder

Autodetected by default. Encode using -codec:v h264_videotoolbox.

Signed-off-by: Rick Kern <kernrj@gmail.com>
Signed-off-by: wm4 <nfxjfg@googlemail.com>

5 files changed, 1361 insertions, 7 deletions

diff --git a/MAINTAINERS b/MAINTAINERS
index 155642b6c0..a62726dba3 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -279,6 +279,7 @@ Codecs:
   vc2*                                  Rostislav Pehlivanov
   vcr1.c                                Michael Niedermayer
   vda_h264_dec.c                        Xidorn Quan
+  videotoolboxenc.c                     Rick Kern
   vima.c                                Paul B Mahol
   vmnc.c                                Kostya Shishkov
   vorbisdec.c                           Denes Balatoni, David Conrad
diff --git a/configure b/configure
index 8491fa103e..81769ee0f2 100755
--- a/configure
+++ b/configure
@@ -155,7 +155,6 @@ Hardware accelerators:
   --disable-vaapi          disable VAAPI code [autodetect]
   --disable-vda            disable VDA code [autodetect]
   --disable-vdpau          disable VDPAU code [autodetect]
-  --enable-videotoolbox    enable VideoToolbox code [autodetect]
 
 Individual component options:
   --disable-everything     disable all components listed below
@@ -289,6 +288,7 @@ External library support:
   --disable-sdl            disable sdl [autodetect]
   --disable-securetransport disable Secure Transport, needed for TLS support
                            on OSX if openssl and gnutls are not used [autodetect]
+  --disable-videotoolbox   disable VideoToolbox code [autodetect]
   --enable-x11grab         enable X11 grabbing (legacy) [no]
   --disable-xlib           disable xlib [autodetect]
   --disable-zlib           disable zlib [autodetect]
@@ -1509,6 +1509,7 @@ EXTERNAL_LIBRARY_LIST="
     schannel
     sdl
     securetransport
+    videotoolbox
     x11grab
     xlib
     zlib
@@ -1540,7 +1541,7 @@ HWACCEL_LIST="
     vaapi
     vda
     vdpau
-    videotoolbox
+    videotoolbox_hwaccel
     xvmc
 "
 
@@ -2484,11 +2485,13 @@ crystalhd_deps="libcrystalhd_libcrystalhd_if_h"
 d3d11va_deps="d3d11_h dxva_h ID3D11VideoDecoder ID3D11VideoContext"
 dxva2_deps="dxva2api_h DXVA2_ConfigPictureDecode"
 vaapi_deps="va_va_h"
-vda_deps="VideoDecodeAcceleration_VDADecoder_h pthreads"
-vda_extralibs="-framework CoreFoundation -framework VideoDecodeAcceleration -framework QuartzCore"
+vda_framework_deps="VideoDecodeAcceleration_VDADecoder_h"
+vda_framework_extralibs="-framework VideoDecodeAcceleration"
+vda_deps="vda_framework pthreads"
+vda_extralibs="-framework CoreFoundation -framework QuartzCore"
 vdpau_deps="vdpau_vdpau_h vdpau_vdpau_x11_h"
-videotoolbox_deps="VideoToolbox_VideoToolbox_h pthreads"
-videotoolbox_extralibs="-framework CoreFoundation -framework VideoToolbox -framework CoreMedia -framework QuartzCore -framework CoreVideo"
+videotoolbox_hwaccel_deps="videotoolbox pthreads"
+videotoolbox_hwaccel_extralibs="-framework QuartzCore"
 xvmc_deps="X11_extensions_XvMClib_h"
 
 h263_vaapi_hwaccel_deps="vaapi"
@@ -2611,6 +2614,8 @@ mjpeg2jpeg_bsf_select="jpegtables"
 
 # external libraries
 chromaprint_muxer_deps="chromaprint"
+h264_videotoolbox_encoder_deps="videotoolbox_encoder pthreads"
+h264_videotoolbox_encoder_select="bzlib zlib iconv"
 libcelt_decoder_deps="libcelt"
 libdcadec_decoder_deps="libdcadec"
 libfaac_encoder_deps="libfaac"
@@ -2672,6 +2677,10 @@ libzvbi_teletext_decoder_deps="libzvbi"
 nvenc_encoder_deps="nvenc"
 nvenc_h264_encoder_deps="nvenc"
 nvenc_hevc_encoder_deps="nvenc"
+videotoolbox_deps="VideoToolbox_VideoToolbox_h"
+videotoolbox_extralibs="-framework CoreFoundation -framework VideoToolbox -framework CoreMedia -framework CoreVideo"
+videotoolbox_encoder_deps="videotoolbox VTCompressionSessionPrepareToEncodeFrames"
+videotoolbox_encoder_suggest="vda_framework"
 
 # demuxers / muxers
 ac3_demuxer_select="ac3_parser"
@@ -3052,9 +3061,11 @@ sws_max_filter_size_default=256
 set_default sws_max_filter_size
 
 # Enable hwaccels by default.
-enable d3d11va dxva2 vaapi vda vdpau videotoolbox xvmc
+enable d3d11va dxva2 vaapi vda vdpau videotoolbox_hwaccel xvmc
 enable xlib
 
+enable vda_framework videotoolbox videotoolbox_encoder
+
 # build settings
 SHFLAGS='-shared -Wl,-soname,$$(@F)'
 LIBPREF="lib"
@@ -5449,6 +5460,7 @@ check_header vdpau/vdpau.h
 check_header vdpau/vdpau_x11.h
 check_header VideoDecodeAcceleration/VDADecoder.h
 check_header VideoToolbox/VideoToolbox.h
+check_func_headers VideoToolbox/VTCompressionSession.h VTCompressionSessionPrepareToEncodeFrames -framework VideoToolbox
 check_header windows.h
 check_header X11/extensions/XvMClib.h
 check_header asm/types.h
diff --git a/libavcodec/Makefile b/libavcodec/Makefile
index 667e2578d0..bbca908b2f 100644
--- a/libavcodec/Makefile
+++ b/libavcodec/Makefile
@@ -69,6 +69,7 @@ OBJS-$(CONFIG_H264CHROMA)              += h264chroma.o
 OBJS-$(CONFIG_H264DSP)                 += h264dsp.o h264idct.o
 OBJS-$(CONFIG_H264PRED)                += h264pred.o
 OBJS-$(CONFIG_H264QPEL)                += h264qpel.o
+OBJS-$(CONFIG_H264_VIDEOTOOLBOX_ENCODER) += videotoolboxenc.o
 OBJS-$(CONFIG_HPELDSP)                 += hpeldsp.o
 OBJS-$(CONFIG_HUFFMAN)                 += huffman.o
 OBJS-$(CONFIG_HUFFYUVDSP)              += huffyuvdsp.o
diff --git a/libavcodec/allcodecs.c b/libavcodec/allcodecs.c
index 2097db03b5..91c1c5c9f3 100644
--- a/libavcodec/allcodecs.c
+++ b/libavcodec/allcodecs.c
@@ -604,6 +604,7 @@ void avcodec_register_all(void)
      * above is available */
     REGISTER_ENCODER(LIBOPENH264,       libopenh264);
     REGISTER_ENCODER(H264_QSV,          h264_qsv);
+    REGISTER_ENCODER(H264_VIDEOTOOLBOX, h264_videotoolbox);
     REGISTER_ENCODER(NVENC,             nvenc);
     REGISTER_ENCODER(NVENC_H264,        nvenc_h264);
     REGISTER_ENCODER(NVENC_HEVC,        nvenc_hevc);
diff --git a/libavcodec/videotoolboxenc.c b/libavcodec/videotoolboxenc.c
new file mode 100644
index 0000000000..bbecb24f11
--- /dev/null
+++ b/libavcodec/videotoolboxenc.c
@@ -0,0 +1,1339 @@
+/*
+ * copyright (c) 2015 Rick Kern <kernrj@gmail.com>
+ *
+ * This file is part of FFmpeg.
+ *
+ * FFmpeg is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * FFmpeg is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with FFmpeg; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+#include <VideoToolbox/VideoToolbox.h>
+#include <CoreVideo/CoreVideo.h>
+#include <CoreMedia/CoreMedia.h>
+#include <TargetConditionals.h>
+#include <Availability.h>
+#include "avcodec.h"
+#include "libavutil/opt.h"
+#include "libavutil/avassert.h"
+#include "libavutil/atomic.h"
+#include "libavutil/avstring.h"
+#include "libavcodec/avcodec.h"
+#include "internal.h"
+#include <pthread.h>
+
+typedef enum VT_H264Profile {
+    H264_PROF_AUTO,
+    H264_PROF_BASELINE,
+    H264_PROF_MAIN,
+    H264_PROF_HIGH,
+    H264_PROF_COUNT
+} VT_H264Profile;
+
+static const uint8_t start_code[] = { 0, 0, 0, 1 };
+
+typedef struct BufNode {
+    CMSampleBufferRef cm_buffer;
+    struct BufNode* next;
+    int error;
+} BufNode;
+
+typedef struct VTEncContext {
+    AVClass *class;
+    VTCompressionSessionRef session;
+
+    pthread_mutex_t lock;
+    pthread_cond_t  cv_sample_sent;
+
+    int async_error;
+
+    BufNode *q_head;
+    BufNode *q_tail;
+
+    int64_t frame_ct_out;
+    int64_t frame_ct_in;
+
+    int64_t first_pts;
+    int64_t dts_delta;
+
+    int64_t profile;
+    int64_t level;
+
+    bool flushing;
+    bool has_b_frames;
+    bool warned_color_range;
+} VTEncContext;
+
+static void set_async_error(VTEncContext *vtctx, int err)
+{
+    BufNode *info;
+
+    pthread_mutex_lock(&vtctx->lock);
+
+    vtctx->async_error = err;
+
+    info = vtctx->q_head;
+    vtctx->q_head = vtctx->q_tail = NULL;
+
+    while (info) {
+        BufNode *next = info->next;
+        CFRelease(info->cm_buffer);
+        av_free(info);
+        info = next;
+    }
+
+    pthread_mutex_unlock(&vtctx->lock);
+}
+
+static int vtenc_q_pop(VTEncContext *vtctx, bool wait, CMSampleBufferRef *buf)
+{
+    BufNode *info;
+
+    pthread_mutex_lock(&vtctx->lock);
+
+    if (vtctx->async_error) {
+        pthread_mutex_unlock(&vtctx->lock);
+        return vtctx->async_error;
+    }
+
+    if (vtctx->flushing && vtctx->frame_ct_in == vtctx->frame_ct_out) {
+        *buf = NULL;
+
+        pthread_mutex_unlock(&vtctx->lock);
+        return 0;
+    }
+
+    while (!vtctx->q_head && !vtctx->async_error && wait) {
+        pthread_cond_wait(&vtctx->cv_sample_sent, &vtctx->lock);
+    }
+
+    if (!vtctx->q_head) {
+        pthread_mutex_unlock(&vtctx->lock);
+        *buf = NULL;
+        return 0;
+    }
+
+    info = vtctx->q_head;
+    vtctx->q_head = vtctx->q_head->next;
+    if (!vtctx->q_head) {
+        vtctx->q_tail = NULL;
+    }
+
+    pthread_mutex_unlock(&vtctx->lock);
+
+    *buf = info->cm_buffer;
+    av_free(info);
+
+    vtctx->frame_ct_out++;
+
+    return 0;
+}
+
+static void vtenc_q_push(VTEncContext *vtctx, CMSampleBufferRef buffer)
+{
+    BufNode *info = av_malloc(sizeof(BufNode));
+    if (!info) {
+        set_async_error(vtctx, AVERROR(ENOMEM));
+        return;
+    }
+
+    CFRetain(buffer);
+    info->cm_buffer = buffer;
+    info->next = NULL;
+
+    pthread_mutex_lock(&vtctx->lock);
+    pthread_cond_signal(&vtctx->cv_sample_sent);
+
+    if (!vtctx->q_head) {
+        vtctx->q_head = info;
+    } else {
+        vtctx->q_tail->next = info;
+    }
+
+    vtctx->q_tail = info;
+
+    pthread_mutex_unlock(&vtctx->lock);
+}
+
+static CMVideoCodecType get_cm_codec_type(enum AVCodecID id)
+{
+    switch (id) {
+    case AV_CODEC_ID_H264: return kCMVideoCodecType_H264;
+    default:               return 0;
+    }
+}
+
+static void vtenc_free_block(void *opaque, uint8_t *data)
+{
+    CMBlockBufferRef block = opaque;
+    CFRelease(block);
+}
+
+/**
+ * Get the parameter sets from a CMSampleBufferRef.
+ * @param dst If *dst isn't NULL, the parameters are copied into existing
+ *            memory. *dst_size must be set accordingly when *dst != NULL.
+ *            If *dst is NULL, it will be allocated.
+ *            In all cases, *dst_size is set to the number of bytes used starting
+ *            at *dst.
+ */
+static int get_params_size(
+    AVCodecContext              *avctx,
+    CMVideoFormatDescriptionRef vid_fmt,
+    size_t                      *size)
+{
+    size_t total_size = 0;
+    size_t ps_count;
+    size_t i;
+    int status;
+    status = CMVideoFormatDescriptionGetH264ParameterSetAtIndex(vid_fmt,
+                                                                0,
+                                                                NULL,
+                                                                NULL,
+                                                                &ps_count,
+                                                                NULL);
+    if (status) {
+        av_log(avctx, AV_LOG_ERROR, "Error getting parameter set count: %d\n", status);
+        return AVERROR_EXTERNAL;
+    }
+
+    for(i = 0; i < ps_count; i++){
+        const uint8_t *ps;
+        size_t ps_size;
+        status = CMVideoFormatDescriptionGetH264ParameterSetAtIndex(vid_fmt,
+                                                                    i,
+                                                                    &ps,
+                                                                    &ps_size,
+                                                                    NULL,
+                                                                    NULL);
+        if(status){
+            av_log(avctx, AV_LOG_ERROR, "Error getting parameter set size for index %zd: %d\n", i, status);
+            return AVERROR_EXTERNAL;
+        }
+
+        total_size += ps_size + sizeof(start_code);
+    }
+
+    *size = total_size;
+    return 0;
+}
+
+static int copy_param_sets(
+    AVCodecContext              *avctx,
+    CMVideoFormatDescriptionRef vid_fmt,
+    uint8_t                     *dst,
+    size_t                      dst_size)
+{
+    size_t ps_count;
+    int status;
+    size_t offset = 0;
+    size_t i;
+
+    status = CMVideoFormatDescriptionGetH264ParameterSetAtIndex(vid_fmt,
+                                                                0,
+                                                                NULL,
+                                                                NULL,
+                                                                &ps_count,
+                                                                NULL);
+    if (status) {
+        av_log(avctx, AV_LOG_ERROR, "Error getting parameter set count for copying: %d\n", status);
+        return AVERROR_EXTERNAL;
+    }
+
+    for (i = 0; i < ps_count; i++) {
+        const uint8_t *ps;
+        size_t ps_size;
+        size_t next_offset;
+
+        status = CMVideoFormatDescriptionGetH264ParameterSetAtIndex(vid_fmt,
+                                                                    i,
+                                                                    &ps,
+                                                                    &ps_size,
+                                                                    NULL,
+                                                                    NULL);
+        if (status) {
+            av_log(avctx, AV_LOG_ERROR, "Error getting parameter set data for index %zd: %d\n", i, status);
+            return AVERROR_EXTERNAL;
+        }
+
+        next_offset = offset + sizeof(start_code) + ps_size;
+        if (dst_size < next_offset) {
+            av_log(avctx, AV_LOG_ERROR, "Error: buffer too small for parameter sets.\n");
+            return AVERROR_BUFFER_TOO_SMALL;
+        }
+
+        memcpy(dst + offset, start_code, sizeof(start_code));
+        offset += sizeof(start_code);
+
+        memcpy(dst + offset, ps, ps_size);
+        offset = next_offset;
+    }
+
+    return 0;
+}
+
+static int set_extradata(AVCodecContext *avctx, CMSampleBufferRef sample_buffer)
+{
+    CMVideoFormatDescriptionRef vid_fmt;
+    size_t total_size;
+    int status;
+
+    vid_fmt = CMSampleBufferGetFormatDescription(sample_buffer);
+    if (!vid_fmt) {
+        av_log(avctx, AV_LOG_ERROR, "No video format.\n");
+        return AVERROR_EXTERNAL;
+    }
+
+    status = get_params_size(avctx, vid_fmt, &total_size);
+    if (status) {
+        av_log(avctx, AV_LOG_ERROR, "Could not get parameter sets.\n");
+        return status;
+    }
+
+    avctx->extradata = av_malloc(total_size);
+    if (!avctx->extradata) {
+        return AVERROR(ENOMEM);
+    }
+    avctx->extradata_size = total_size;
+
+    status = copy_param_sets(avctx, vid_fmt, avctx->extradata, total_size);
+
+    if (status) {
+        av_log(avctx, AV_LOG_ERROR, "Could not copy param sets.\n");
+        return status;
+    }
+
+    return 0;
+}
+
+static void vtenc_output_callback(
+    void *CM_NULLABLE ctx,
+    void *sourceFrameCtx,
+    OSStatus status,
+    VTEncodeInfoFlags flags,
+    CM_NULLABLE CMSampleBufferRef sample_buffer)
+{
+    AVCodecContext *avctx = ctx;
+    VTEncContext   *vtctx = avctx->priv_data;
+
+    if (vtctx->async_error) {
+        if(sample_buffer) CFRelease(sample_buffer);
+        return;
+    }
+
+    if (status || !sample_buffer) {
+        av_log(avctx, AV_LOG_ERROR, "Error encoding frame: %d\n", (int)status);
+        set_async_error(vtctx, AVERROR_EXTERNAL);
+        return;
+    }
+
+    if (!avctx->extradata && (avctx->flags & AV_CODEC_FLAG_GLOBAL_HEADER)) {
+        int set_status = set_extradata(avctx, sample_buffer);
+        if (set_status) {
+            set_async_error(vtctx, set_status);
+            return;
+        }
+    }
+
+    vtenc_q_push(vtctx, sample_buffer);
+}
+
+static int get_length_code_size(
+    AVCodecContext    *avctx,
+    CMSampleBufferRef sample_buffer,
+    size_t            *size)
+{
+    CMVideoFormatDescriptionRef vid_fmt;
+    int isize;
+    int status;
+
+    vid_fmt = CMSampleBufferGetFormatDescription(sample_buffer);
+    if (!vid_fmt) {
+        av_log(avctx, AV_LOG_ERROR, "Error getting buffer format description.\n");
+        return AVERROR_EXTERNAL;
+    }
+
+    status = CMVideoFormatDescriptionGetH264ParameterSetAtIndex(vid_fmt,
+                                                                0,
+                                                                NULL,
+                                                                NULL,
+                                                                NULL,
+                                                                &isize);
+    if (status) {
+        av_log(avctx, AV_LOG_ERROR, "Error getting length code size: %d\n", status);
+        return AVERROR_EXTERNAL;
+    }
+
+    *size = isize;
+    return 0;
+}
+
+/*
+ * Returns true on success.
+ *
+ * If profile_level_val is NULL and this method returns true, don't specify the
+ * profile/level to the encoder.
+ */
+static bool get_vt_profile_level(AVCodecContext *avctx,
+                                 CFStringRef    *profile_level_val)
+{
+    VTEncContext *vtctx = avctx->priv_data;
+    int64_t profile = vtctx->profile;
+
+    if (profile == H264_PROF_AUTO && vtctx->level) {
+        //Need to pick a profile if level is not auto-selected.
+        profile = vtctx->has_b_frames ? H264_PROF_MAIN : H264_PROF_BASELINE;
+    }
+
+    *profile_level_val = NULL;
+
+    switch (profile) {
+        case H264_PROF_AUTO:
+            return true;
+
+        case H264_PROF_BASELINE:
+            switch (vtctx->level) {
+                case  0: *profile_level_val = kVTProfileLevel_H264_Baseline_AutoLevel; break;
+                case 13: *profile_level_val = kVTProfileLevel_H264_Baseline_1_3;       break;
+                case 30: *profile_level_val = kVTProfileLevel_H264_Baseline_3_0;       break;
+                case 31: *profile_level_val = kVTProfileLevel_H264_Baseline_3_1;       break;
+                case 32: *profile_level_val = kVTProfileLevel_H264_Baseline_3_2;       break;
+                case 40: *profile_level_val = kVTProfileLevel_H264_Baseline_4_0;       break;
+                case 41: *profile_level_val = kVTProfileLevel_H264_Baseline_4_1;       break;
+                case 42: *profile_level_val = kVTProfileLevel_H264_Baseline_4_2;       break;
+                case 50: *profile_level_val = kVTProfileLevel_H264_Baseline_5_0;       break;
+                case 51: *profile_level_val = kVTProfileLevel_H264_Baseline_5_1;       break;
+                case 52: *profile_level_val = kVTProfileLevel_H264_Baseline_5_2;       break;
+            }
+            break;
+
+        case H264_PROF_MAIN:
+            switch (vtctx->level) {
+                case  0: *profile_level_val = kVTProfileLevel_H264_Main_AutoLevel; break;
+                case 30: *profile_level_val = kVTProfileLevel_H264_Main_3_0;       break;
+                case 31: *profile_level_val = kVTProfileLevel_H264_Main_3_1;       break;
+                case 32: *profile_level_val = kVTProfileLevel_H264_Main_3_2;       break;
+                case 40: *profile_level_val = kVTProfileLevel_H264_Main_4_0;       break;
+                case 41: *profile_level_val = kVTProfileLevel_H264_Main_4_1;       break;
+                case 42: *profile_level_val = kVTProfileLevel_H264_Main_4_2;       break;
+                case 50: *profile_level_val = kVTProfileLevel_H264_Main_5_0;       break;
+                case 51: *profile_level_val = kVTProfileLevel_H264_Main_5_1;       break;
+                case 52: *profile_level_val = kVTProfileLevel_H264_Main_5_2;       break;
+            }
+            break;
+
+        case H264_PROF_HIGH:
+            switch (vtctx->level) {
+                case  0: *profile_level_val = kVTProfileLevel_H264_High_AutoLevel; break;
+                case 30: *profile_level_val = kVTProfileLevel_H264_High_3_0;       break;
+                case 31: *profile_level_val = kVTProfileLevel_H264_High_3_1;       break;
+                case 32: *profile_level_val = kVTProfileLevel_H264_High_3_2;       break;
+                case 40: *profile_level_val = kVTProfileLevel_H264_High_4_0;       break;
+                case 41: *profile_level_val = kVTProfileLevel_H264_High_4_1;       break;
+                case 42: *profile_level_val = kVTProfileLevel_H264_High_4_2;       break;
+                case 50: *profile_level_val = kVTProfileLevel_H264_High_5_0;       break;
+                case 51: *profile_level_val = kVTProfileLevel_H264_High_5_1;       break;
+                case 52: *profile_level_val = kVTProfileLevel_H264_High_5_2;       break;
+            }
+            break;
+    }
+
+    if (!*profile_level_val) {
+        av_log(avctx, AV_LOG_ERROR, "Invalid Profile/Level.\n");
+        return false;
+    }
+
+    return true;
+}
+
+static av_cold int vtenc_init(AVCodecContext *avctx)
+{
+    CFMutableDictionaryRef enc_info;
+    CMVideoCodecType       codec_type;
+    VTEncContext           *vtctx = avctx->priv_data;
+    CFStringRef            profile_level;
+    SInt32                 bit_rate = avctx->bit_rate;
+    CFNumberRef            bit_rate_num;
+    int                    status;
+
+    codec_type = get_cm_codec_type(avctx->codec_id);
+    if (!codec_type) {
+        av_log(avctx, AV_LOG_ERROR, "Error: no mapping for AVCodecID %d\n", avctx->codec_id);
+        return AVERROR(EINVAL);
+    }
+
+    vtctx->has_b_frames = avctx->has_b_frames || avctx->max_b_frames > 0;
+    if(vtctx->has_b_frames && vtctx->profile == H264_PROF_BASELINE){
+        av_log(avctx, AV_LOG_WARNING, "Cannot use B-frames with baseline profile. Output will not contain B-frames.\n");
+        vtctx->has_b_frames = false;
+    }
+
+    if (!get_vt_profile_level(avctx, &profile_level)) return AVERROR(EINVAL);
+
+    vtctx->session = NULL;
+
+    enc_info = CFDictionaryCreateMutable(
+        kCFAllocatorDefault,
+        20,
+        &kCFCopyStringDictionaryKeyCallBacks,
+        &kCFTypeDictionaryValueCallBacks
+    );
+
+    if (!enc_info) return AVERROR(ENOMEM);
+
+#if !TARGET_OS_IPHONE
+    CFDictionarySetValue(enc_info, kVTVideoEncoderSpecification_RequireHardwareAcceleratedVideoEncoder, kCFBooleanTrue);
+    CFDictionarySetValue(enc_info, kVTVideoEncoderSpecification_EnableHardwareAcceleratedVideoEncoder,  kCFBooleanTrue);
+#endif
+
+    status = VTCompressionSessionCreate(
+        kCFAllocatorDefault,
+        avctx->width,
+        avctx->height,
+        codec_type,
+        enc_info,
+        NULL,
+        kCFAllocatorDefault,
+        vtenc_output_callback,
+        avctx,
+        &vtctx->session
+    );
+
+#if !TARGET_OS_IPHONE
+    if (status != 0 || !vtctx->session) {
+        CFDictionaryRemoveValue(enc_info, kVTVideoEncoderSpecification_RequireHardwareAcceleratedVideoEncoder);
+
+        status = VTCompressionSessionCreate(
+            kCFAllocatorDefault,
+            avctx->width,
+            avctx->height,
+            codec_type,
+            enc_info,
+            NULL,
+            kCFAllocatorDefault,
+            vtenc_output_callback,
+            avctx,
+            &vtctx->session
+        );
+    }
+#endif
+
+    CFRelease(enc_info);
+
+    if (status || !vtctx->session) {
+        av_log(avctx, AV_LOG_ERROR, "Error: cannot create compression session: %d\n", status);
+        return AVERROR_EXTERNAL;
+    }
+
+    bit_rate_num = CFNumberCreate(kCFAllocatorDefault,
+                                  kCFNumberSInt32Type,
+                                  &bit_rate);
+    if (!bit_rate_num) return AVERROR(ENOMEM);
+
+    status = VTSessionSetProperty(vtctx->session,
+                                  kVTCompressionPropertyKey_AverageBitRate,
+                                  bit_rate_num);
+    CFRelease(bit_rate_num);
+
+    if (status) {
+        av_log(avctx, AV_LOG_ERROR, "Error setting bitrate property: %d\n", status);
+        return AVERROR_EXTERNAL;
+    }
+
+    if (profile_level) {
+        status = VTSessionSetProperty(vtctx->session,
+                                      kVTCompressionPropertyKey_ProfileLevel,
+                                      profile_level);
+        if (status) {
+            av_log(avctx, AV_LOG_ERROR, "Error setting profile/level property: %d\n", status);
+            return AVERROR_EXTERNAL;
+        }
+    }
+
+    if (avctx->gop_size > 0) {
+        CFNumberRef interval = CFNumberCreate(kCFAllocatorDefault,
+                                              kCFNumberIntType,
+                                              &avctx->gop_size);
+        status = VTSessionSetProperty(vtctx->session,
+                                      kVTCompressionPropertyKey_MaxKeyFrameInterval,
+                                      interval);
+
+        if (status) {
+            av_log(avctx, AV_LOG_ERROR, "Error setting 'max key-frame interval' property: %d\n", status);
+            return AVERROR_EXTERNAL;
+        }
+    }
+
+    if (!vtctx->has_b_frames) {
+        status = VTSessionSetProperty(vtctx->session,
+                                      kVTCompressionPropertyKey_AllowFrameReordering,
+                                      kCFBooleanFalse);
+
+        if (status) {
+            av_log(avctx, AV_LOG_ERROR, "Error setting 'allow frame reordering' property: %d\n", status);
+            return AVERROR_EXTERNAL;
+        }
+    }
+
+    status = VTCompressionSessionPrepareToEncodeFrames(vtctx->session);
+    if (status) {
+        av_log(avctx, AV_LOG_ERROR, "Error: cannot prepare encoder: %d\n", status);
+        return AVERROR_EXTERNAL;
+    }
+
+    pthread_mutex_init(&vtctx->lock, NULL);
+    pthread_cond_init(&vtctx->cv_sample_sent, NULL);
+    vtctx->dts_delta = vtctx->has_b_frames ? -1 : 0;
+
+    return 0;
+}
+
+static void vtenc_get_frame_info(CMSampleBufferRef buffer, bool *is_key_frame)
+{
+    CFArrayRef      attachments;
+    CFDictionaryRef attachment;
+    CFBooleanRef    not_sync;
+    CFIndex         len;
+
+    attachments = CMSampleBufferGetSampleAttachmentsArray(buffer, false);
+    len = !attachments ? 0 : CFArrayGetCount(attachments);
+
+    if (!len) {
+        *is_key_frame = true;
+        return;
+    }
+
+    attachment = CFArrayGetValueAtIndex(attachments, 0);
+
+    if (CFDictionaryGetValueIfPresent(attachment,
+                                      kCMSampleAttachmentKey_NotSync,
+                                      (const void **)&not_sync))
+    {
+        *is_key_frame = !CFBooleanGetValue(not_sync);
+    } else {
+        *is_key_frame = true;
+    }
+}
+
+/**
+ * Replaces length codes with H.264 Annex B start codes.
+ * length_code_size must equal sizeof(start_code).
+ * On failure, the contents of data may have been modified.
+ *
+ * @param length_code_size Byte length of each length code
+ * @param data Call with NAL units prefixed with length codes.
+ *             On success, the length codes are replace with
+ *             start codes.
+ * @param size Length of data, excluding any padding.
+ * @return 0 on success
+ *         AVERROR_BUFFER_TOO_SMALL if length code size is smaller
+ *         than a start code or if a length_code in data specifies
+ *         data beyond the end of its buffer.
+ */
+static int replace_length_codes(size_t  length_code_size,
+                                uint8_t *data,
+                                size_t  size)
+{
+    size_t remaining_size = size;
+
+    if (length_code_size != sizeof(start_code)) {
+        av_log(NULL, AV_LOG_ERROR, "Start code size and length code size not equal.\n");
+        return AVERROR_BUFFER_TOO_SMALL;
+    }
+
+    while (remaining_size > 0) {
+        size_t box_len = 0;
+        size_t i;
+
+        for (i = 0; i < length_code_size; i++) {
+            box_len <<= 8;
+            box_len |= data[i];
+        }
+
+        if (remaining_size < box_len + sizeof(start_code)) {
+            av_log(NULL, AV_LOG_ERROR, "Length is out of range.\n");
+            AVERROR_BUFFER_TOO_SMALL;
+        }
+
+        memcpy(data, start_code, sizeof(start_code));
+        data += box_len + sizeof(start_code);
+        remaining_size -= box_len + sizeof(start_code);
+    }
+
+    return 0;
+}
+
+/**
+ * Copies NAL units and replaces length codes with
+ * H.264 Annex B start codes. On failure, the contents of
+ * dst_data may have been modified.
+ *
+ * @param length_code_size Byte length of each length code
+ * @param src_data NAL units prefixed with length codes.
+ * @param src_size Length of buffer, excluding any padding.
+ * @param dst_data Must be zeroed before calling this function.
+ *                 Contains the copied NAL units prefixed with
+ *                 start codes when the function returns
+ *                 successfully.
+ * @param dst_size Length of dst_data
+ * @return 0 on success
+ *         AVERROR_INVALIDDATA if length_code_size is invalid
+ *         AVERROR_BUFFER_TOO_SMALL if dst_data is too small
+ *         or if a length_code in src_data specifies data beyond
+ *         the end of its buffer.
+ */
+static int copy_replace_length_codes(
+    size_t        length_code_size,
+    const uint8_t *src_data,
+    size_t        src_size,
+    uint8_t       *dst_data,
+    size_t        dst_size)
+{
+    size_t remaining_src_size = src_size;
+    size_t remaining_dst_size = dst_size;
+
+    if (length_code_size > 4) {
+        return AVERROR_INVALIDDATA;
+    }
+
+    while (remaining_src_size > 0) {
+        size_t curr_src_len;
+        size_t curr_dst_len;
+        size_t box_len = 0;
+        size_t i;
+
+        uint8_t       *dst_box;
+        const uint8_t *src_box;
+
+        for (i = 0; i < length_code_size; i++) {
+            box_len <<= 8;
+            box_len |= src_data[i];
+        }
+
+        curr_src_len = box_len + length_code_size;
+        curr_dst_len = box_len + sizeof(start_code);
+
+        if (remaining_src_size < curr_src_len) {
+            return AVERROR_BUFFER_TOO_SMALL;
+        }
+
+        if (remaining_dst_size < curr_dst_len) {
+            return AVERROR_BUFFER_TOO_SMALL;
+        }
+
+        dst_box = dst_data + sizeof(start_code);
+        src_box = src_data + length_code_size;
+
+        memcpy(dst_data, start_code, sizeof(start_code));
+        memcpy(dst_box,  src_box,    box_len);
+
+        src_data += curr_src_len;
+        dst_data += curr_dst_len;
+
+        remaining_src_size -= curr_src_len;
+        remaining_dst_size -= curr_dst_len;
+    }
+
+    return 0;
+}
+
+static int vtenc_cm_to_avpacket(
+    AVCodecContext    *avctx,
+    CMSampleBufferRef sample_buffer,
+    AVPacket          *pkt)
+{
+    VTEncContext *vtctx = avctx->priv_data;
+
+    int     status;
+    bool    is_key_frame;
+    bool    add_header;
+    char    *buf_data;
+    size_t  length_code_size;
+    size_t  header_size = 0;
+    size_t  in_buf_size;
+    int64_t dts_delta;
+    int64_t time_base_num;
+    CMTime  pts;
+    CMTime  dts;
+
+    CMBlockBufferRef            block;
+    CMVideoFormatDescriptionRef vid_fmt;
+
+
+    vtenc_get_frame_info(sample_buffer, &is_key_frame);
+    status = get_length_code_size(avctx, sample_buffer, &length_code_size);
+    if (status) return status;
+
+    add_header = is_key_frame && !(avctx->flags & AV_CODEC_FLAG_GLOBAL_HEADER);
+
+    if (add_header) {
+        vid_fmt = CMSampleBufferGetFormatDescription(sample_buffer);
+        if (!vid_fmt) {
+            av_log(avctx, AV_LOG_ERROR, "Cannot get format description.\n");
+        }
+
+        int status = get_params_size(avctx, vid_fmt, &header_size);
+        if (status) return status;
+    }
+
+    block = CMSampleBufferGetDataBuffer(sample_buffer);
+    if (!block) {
+        av_log(avctx, AV_LOG_ERROR, "Could not get block buffer from sample buffer.\n");
+        return AVERROR_EXTERNAL;
+    }
+
+
+    status = CMBlockBufferGetDataPointer(block, 0, &in_buf_size, NULL, &buf_data);
+    if (status) {
+        av_log(avctx, AV_LOG_ERROR, "Error: cannot get data pointer: %d\n", status);
+        return AVERROR_EXTERNAL;
+    }
+
+    size_t out_buf_size = header_size + in_buf_size;
+    bool can_reuse_cmbuffer = !add_header &&
+                              !pkt->data  &&
+                              length_code_size == sizeof(start_code);
+
+    av_init_packet(pkt);
+
+    if (can_reuse_cmbuffer) {
+        AVBufferRef* buf_ref = av_buffer_create(
+            buf_data,
+            out_buf_size,
+            vtenc_free_block,
+            block,
+            0
+        );
+
+        if (!buf_ref) return AVERROR(ENOMEM);
+
+        CFRetain(block);
+
+        pkt->buf  = buf_ref;
+        pkt->data = buf_data;
+        pkt->size = in_buf_size;
+
+        status = replace_length_codes(length_code_size, pkt->data, pkt->size);
+        if (status) {
+            av_log(avctx, AV_LOG_ERROR, "Error replacing length codes: %d\n", status);
+            return status;
+        }
+    } else {
+        if (!pkt->data) {
+            status = av_new_packet(pkt, out_buf_size);
+            if(status) return status;
+        }
+
+        if (pkt->size < out_buf_size) {
+            av_log(avctx, AV_LOG_ERROR, "Error: packet's buffer is too small.\n");
+            return AVERROR_BUFFER_TOO_SMALL;
+        }
+
+        if (add_header) {
+            status = copy_param_sets(avctx, vid_fmt, pkt->data, out_buf_size);
+            if(status) return status;
+        }
+
+        status = copy_replace_length_codes(
+            length_code_size,
+            buf_data,
+            in_buf_size,
+            pkt->data + header_size,
+            pkt->size - header_size
+        );
+
+        if (status) {
+            av_log(avctx, AV_LOG_ERROR, "Error copying packet data: %d", status);
+            return status;
+        }
+    }
+
+    if (is_key_frame) {
+        pkt->flags |= AV_PKT_FLAG_KEY;
+    }
+
+    pts = CMSampleBufferGetPresentationTimeStamp(sample_buffer);
+    dts = CMSampleBufferGetDecodeTimeStamp      (sample_buffer);
+
+    dts_delta = vtctx->dts_delta >= 0 ? vtctx->dts_delta : 0;
+    time_base_num = avctx->time_base.num;
+    pkt->pts = pts.value / time_base_num;
+    pkt->dts = dts.value / time_base_num - dts_delta;
+
+    return 0;
+}
+
+/*
+ * contiguous_buf_size is 0 if not contiguous, and the size of the buffer
+ * containing all planes if so.
+ */
+static int get_cv_pixel_info(
+    AVCodecContext *avctx,
+    const AVFrame  *frame,
+    int            *color,
+    int            *plane_count,
+    size_t         *widths,
+    size_t         *heights,
+    size_t         *strides,
+    size_t         *contiguous_buf_size)
+{
+    VTEncContext *vtctx = avctx->priv_data;
+    int av_format       = frame->format;
+    int av_color_range  = av_frame_get_color_range(frame);
+    int i;
+
+    switch (av_format) {
+    case AV_PIX_FMT_NV12:
+        switch (av_color_range) {
+        case AVCOL_RANGE_MPEG:
+            *color = kCVPixelFormatType_420YpCbCr8BiPlanarVideoRange;
+            break;
+
+        case AVCOL_RANGE_JPEG:
+            *color = kCVPixelFormatType_420YpCbCr8BiPlanarFullRange;
+            break;
+
+        default:
+            if (!vtctx->warned_color_range) {
+                vtctx->warned_color_range = true;
+                av_log(avctx, AV_LOG_WARNING, "Color range not set for NV12. Using MPEG range.\n");
+            }
+            *color = kCVPixelFormatType_420YpCbCr8BiPlanarVideoRange;
+        }
+
+        *plane_count = 2;
+
+        widths [0] = avctx->width;
+        heights[0] = avctx->height;
+        strides[0] = frame ? frame->linesize[0] : avctx->width;
+
+        widths [1] = (avctx->width  + 1) / 2;
+        heights[1] = (avctx->height + 1) / 2;
+        strides[1] = frame ? frame->linesize[1] : (avctx->width + 1) & -2;
+        break;
+
+    case AV_PIX_FMT_YUV420P:
+        switch (av_color_range) {
+        case AVCOL_RANGE_MPEG:
+            *color = kCVPixelFormatType_420YpCbCr8Planar;
+            break;
+
+        case AVCOL_RANGE_JPEG:
+            *color = kCVPixelFormatType_420YpCbCr8PlanarFullRange;
+            break;
+
+        default:
+            if (!vtctx->warned_color_range) {
+                vtctx->warned_color_range = true;
+                av_log(avctx, AV_LOG_WARNING, "Color range not set for YUV 4:2:0. Using MPEG range.\n");
+            }
+            *color = kCVPixelFormatType_420YpCbCr8Planar;
+        }
+
+        *plane_count = 3;
+
+        widths [0] = avctx->width;
+        heights[0] = avctx->height;
+        strides[0] = frame ? frame->linesize[0] : avctx->width;
+
+        widths [1] = (avctx->width  + 1) / 2;
+        heights[1] = (avctx->height + 1) / 2;
+        strides[1] = frame ? frame->linesize[1] : (avctx->width + 1) / 2;
+
+        widths [2] = (avctx->width  + 1) / 2;
+        heights[2] = (avctx->height + 1) / 2;
+        strides[2] = frame ? frame->linesize[2] : (avctx->width + 1) / 2;
+        break;
+
+    default: return AVERROR(EINVAL);
+    }
+
+    *contiguous_buf_size = 0;
+    for (i = 0; i < *plane_count; i++) {
+        if (i < *plane_count - 1 &&
+            frame->data[i] + strides[i] * heights[i] != frame->data[i + 1]) {
+            *contiguous_buf_size = 0;
+            break;
+        }
+
+        *contiguous_buf_size += strides[i] * heights[i];
+    }
+
+    return 0;
+}
+
+#if !TARGET_OS_IPHONE
+//Not used on iOS - frame is always copied.
+static void free_avframe(
+    void       *CV_NULLABLE release_ctx,
+    const void *CV_NULLABLE data,
+    size_t                  size,
+    size_t                  plane_count,
+    const void *CV_NULLABLE plane_addresses[])
+{
+    AVFrame *frame = release_ctx;
+    av_frame_free(&frame);
+}
+#else
+//Not used on OSX - frame is never copied.
+static int copy_avframe_to_pixel_buffer(AVCodecContext   *avctx,
+                                        const AVFrame    *frame,
+                                        CVPixelBufferRef cv_img,
+                                        const size_t     *plane_strides,
+                                        const size_t     *plane_rows)
+{
+    int i, j;
+    size_t plane_count;
+    int status;
+    int rows;
+    int src_stride;
+    int dst_stride;
+    uint8_t *src_addr;
+    uint8_t *dst_addr;
+    size_t copy_bytes;
+
+    status = CVPixelBufferLockBaseAddress(cv_img, 0);
+    if (status) {
+        av_log(
+            avctx,
+            AV_LOG_ERROR,
+            "Error: Could not lock base address of CVPixelBuffer: %d.\n",
+            status
+        );
+    }
+
+    if (CVPixelBufferIsPlanar(cv_img)) {
+        plane_count = CVPixelBufferGetPlaneCount(cv_img);
+        for (i = 0; frame->data[i]; i++) {
+            if (i == plane_count) {
+                CVPixelBufferUnlockBaseAddress(cv_img, 0);
+                av_log(avctx,
+                    AV_LOG_ERROR,
+                    "Error: different number of planes in AVFrame and CVPixelBuffer.\n"
+                );
+
+                return AVERROR_EXTERNAL;
+            }
+
+            dst_addr = (uint8_t*)CVPixelBufferGetBaseAddressOfPlane(cv_img, i);
+            src_addr = (uint8_t*)frame->data[i];
+            dst_stride = CVPixelBufferGetBytesPerRowOfPlane(cv_img, i);
+            src_stride = plane_strides[i];
+            rows = plane_rows[i];
+
+            if (dst_stride == src_stride) {
+                memcpy(dst_addr, src_addr, src_stride * rows);
+            } else {
+                copy_bytes = dst_stride < src_stride ? dst_stride : src_stride;
+
+                for (j = 0; j < rows; j++) {
+                    memcpy(dst_addr + j * dst_stride, src_addr + j * src_stride, copy_bytes);
+                }
+            }
+        }
+    } else {
+        if (frame->data[1]) {
+            CVPixelBufferUnlockBaseAddress(cv_img, 0);
+            av_log(avctx,
+                AV_LOG_ERROR,
+                "Error: different number of planes in AVFrame and non-planar CVPixelBuffer.\n"
+            );
+
+            return AVERROR_EXTERNAL;
+        }
+
+        dst_addr = (uint8_t*)CVPixelBufferGetBaseAddress(cv_img);
+        src_addr = (uint8_t*)frame->data[0];
+        dst_stride = CVPixelBufferGetBytesPerRow(cv_img);
+        src_stride = plane_strides[0];
+        rows = plane_rows[0];
+
+        if (dst_stride == src_stride) {
+            memcpy(dst_addr, src_addr, src_stride * rows);
+        } else {
+            copy_bytes = dst_stride < src_stride ? dst_stride : src_stride;
+
+            for (j = 0; j < rows; j++) {
+                memcpy(dst_addr + j * dst_stride, src_addr + j * src_stride, copy_bytes);
+            }
+        }
+    }
+
+    status = CVPixelBufferUnlockBaseAddress(cv_img, 0);
+    if (status) {
+        av_log(avctx, AV_LOG_ERROR, "Error: Could not unlock CVPixelBuffer base address: %d.\n", status);
+        return AVERROR_EXTERNAL;
+    }
+
+    return 0;
+}
+#endif //!TARGET_OS_IPHONE
+
+static int create_cv_pixel_buffer(AVCodecContext   *avctx,
+                                  const AVFrame    *frame,
+                                  CVPixelBufferRef *cv_img)
+{
+    int plane_count;
+    int color;
+    size_t widths [AV_NUM_DATA_POINTERS];
+    size_t heights[AV_NUM_DATA_POINTERS];
+    size_t strides[AV_NUM_DATA_POINTERS];
+    int status;
+    size_t contiguous_buf_size;
+
+    memset(widths,  0, sizeof(widths));
+    memset(heights, 0, sizeof(heights));
+    memset(strides, 0, sizeof(strides));
+
+    status = get_cv_pixel_info(
+        avctx,
+        frame,
+        &color,
+        &plane_count,
+        widths,
+        heights,
+        strides,
+        &contiguous_buf_size
+    );
+
+    if (status) {
+        av_log(
+            avctx,
+            AV_LOG_ERROR,
+            "Error: Cannot convert format %d color_range %d: %d\n",
+            frame->format,
+            av_frame_get_color_range(frame),
+            status
+        );
+
+        return AVERROR_EXTERNAL;
+    }
+
+#if TARGET_OS_IPHONE
+    status = CVPixelBufferCreate(
+        kCFAllocatorDefault,
+        frame->width,
+        frame->height,
+        color,
+        NULL,
+        cv_img
+    );
+
+    if (status) {
+        return AVERROR_EXTERNAL;
+    }
+
+    status = copy_avframe_to_pixel_buffer(avctx, frame, *cv_img, strides, heights);
+    if (status) {
+        CFRelease(*cv_img);
+        *cv_img = NULL;
+        return status;
+    }
+#else
+    AVFrame *enc_frame = av_frame_alloc();
+    if (!enc_frame) return AVERROR(ENOMEM);
+
+    status = av_frame_ref(enc_frame, frame);
+    if (status) {
+        av_frame_free(&enc_frame);
+        return status;
+    }
+
+    status = CVPixelBufferCreateWithPlanarBytes(
+        kCFAllocatorDefault,
+        enc_frame->width,
+        enc_frame->height,
+        color,
+        NULL,
+        contiguous_buf_size,
+        plane_count,
+        (void **)enc_frame->data,
+        widths,
+        heights,
+        strides,
+        free_avframe,
+        enc_frame,
+        NULL,
+        cv_img
+    );
+
+    if (status) {
+        av_log(avctx, AV_LOG_ERROR, "Error: Could not create CVPixelBuffer: %d\n", status);
+        return AVERROR_EXTERNAL;
+    }
+#endif
+
+    return 0;
+}
+
+static int vtenc_send_frame(AVCodecContext *avctx,
+                            VTEncContext   *vtctx,
+                            const AVFrame  *frame)
+{
+    CMTime time;
+    CVPixelBufferRef cv_img = NULL;
+    int status = create_cv_pixel_buffer(avctx, frame, &cv_img);
+
+    if (status) return status;
+
+    time = CMTimeMake(frame->pts * avctx->time_base.num, avctx->time_base.den);
+    status = VTCompressionSessionEncodeFrame(
+        vtctx->session,
+        cv_img,
+        time,
+        kCMTimeInvalid,
+        NULL,
+        NULL,
+        NULL
+    );
+
+    CFRelease(cv_img);
+
+    if (status) {
+        av_log(avctx, AV_LOG_ERROR, "Error: cannot encode frame: %d\n", status);
+        return AVERROR_EXTERNAL;
+    }
+
+    return 0;
+}
+
+static av_cold int vtenc_frame(
+    AVCodecContext *avctx,
+    AVPacket       *pkt,
+    const AVFrame  *frame,
+    int            *got_packet)
+{
+    VTEncContext *vtctx = avctx->priv_data;
+    bool get_frame;
+    int status;
+    CMSampleBufferRef buf = NULL;
+
+    if (frame) {
+        status = vtenc_send_frame(avctx, vtctx, frame);
+
+        if (status) {
+            status = AVERROR_EXTERNAL;
+            goto end_nopkt;
+        }
+
+        if (vtctx->frame_ct_in == 0) {
+            vtctx->first_pts = frame->pts;
+        } else if(vtctx->frame_ct_in == 1 && vtctx->has_b_frames) {
+            vtctx->dts_delta = frame->pts - vtctx->first_pts;
+        }
+
+        vtctx->frame_ct_in++;
+    } else if(!vtctx->flushing) {
+        vtctx->flushing = true;
+
+        status = VTCompressionSessionCompleteFrames(vtctx->session,
+                                                    kCMTimeIndefinite);
+
+        if (status) {
+            av_log(avctx, AV_LOG_ERROR, "Error flushing frames: %d\n", status);
+            status = AVERROR_EXTERNAL;
+            goto end_nopkt;
+        }
+    }
+
+    *got_packet = 0;
+    get_frame = vtctx->dts_delta >= 0 || !frame;
+    if (!get_frame) {
+        status = 0;
+        goto end_nopkt;
+    }
+
+    status = vtenc_q_pop(vtctx, !frame, &buf);
+    if (status) goto end_nopkt;
+    if (!buf)   goto end_nopkt;
+
+    status = vtenc_cm_to_avpacket(avctx, buf, pkt);
+    CFRelease(buf);
+    if (status) goto end_nopkt;
+
+    *got_packet = 1;
+    return 0;
+
+end_nopkt:
+    av_packet_unref(pkt);
+    return status;
+}
+
+static av_cold int vtenc_close(AVCodecContext *avctx)
+{
+    VTEncContext *vtctx = avctx->priv_data;
+
+    if(!vtctx->session) return 0;
+
+    VTCompressionSessionInvalidate(vtctx->session);
+    pthread_cond_destroy(&vtctx->cv_sample_sent);
+    pthread_mutex_destroy(&vtctx->lock);
+    CFRelease(vtctx->session);
+    vtctx->session = NULL;
+
+    return 0;
+}
+
+static const enum AVPixelFormat pix_fmts[] = {
+    AV_PIX_FMT_NV12,
+#if !TARGET_OS_IPHONE
+    AV_PIX_FMT_YUV420P,
+#endif
+    AV_PIX_FMT_NONE
+};
+
+#define OFFSET(x) offsetof(VTEncContext, x)
+#define VE AV_OPT_FLAG_VIDEO_PARAM | AV_OPT_FLAG_ENCODING_PARAM
+static const AVOption options[] = {
+    { "profile", "Profile", OFFSET(profile), AV_OPT_TYPE_INT, { .i64 = H264_PROF_AUTO }, H264_PROF_AUTO, H264_PROF_COUNT, VE, "profile" },
+    { "baseline", "Baseline Profile", 0, AV_OPT_TYPE_CONST, { .i64 = H264_PROF_BASELINE }, INT_MIN, INT_MAX, VE, "profile" },
+    { "main",     "Main Profile",     0, AV_OPT_TYPE_CONST, { .i64 = H264_PROF_MAIN     }, INT_MIN, INT_MAX, VE, "profile" },
+    { "high",     "High Profile",     0, AV_OPT_TYPE_CONST, { .i64 = H264_PROF_HIGH     }, INT_MIN, INT_MAX, VE, "profile" },
+
+    { "level", "Level", OFFSET(level), AV_OPT_TYPE_INT, { .i64 = 0 }, 0, 52, VE, "level" },
+    { "1.3", "Level 1.3, only available with Baseline Profile", 0, AV_OPT_TYPE_CONST, { .i64 = 13 }, INT_MIN, INT_MAX, VE, "level" },
+    { "3.0", "Level 3.0", 0, AV_OPT_TYPE_CONST, { .i64 = 30 }, INT_MIN, INT_MAX, VE, "level" },
+    { "3.1", "Level 3.1", 0, AV_OPT_TYPE_CONST, { .i64 = 31 }, INT_MIN, INT_MAX, VE, "level" },
+    { "3.2", "Level 3.2", 0, AV_OPT_TYPE_CONST, { .i64 = 32 }, INT_MIN, INT_MAX, VE, "level" },
+    { "4.0", "Level 4.0", 0, AV_OPT_TYPE_CONST, { .i64 = 40 }, INT_MIN, INT_MAX, VE, "level" },
+    { "4.1", "Level 4.1", 0, AV_OPT_TYPE_CONST, { .i64 = 41 }, INT_MIN, INT_MAX, VE, "level" },
+    { "4.2", "Level 4.2", 0, AV_OPT_TYPE_CONST, { .i64 = 42 }, INT_MIN, INT_MAX, VE, "level" },
+    { "5.0", "Level 5.0", 0, AV_OPT_TYPE_CONST, { .i64 = 50 }, INT_MIN, INT_MAX, VE, "level" },
+    { "5.1", "Level 5.1", 0, AV_OPT_TYPE_CONST, { .i64 = 51 }, INT_MIN, INT_MAX, VE, "level" },
+    { "5.2", "Level 5.2", 0, AV_OPT_TYPE_CONST, { .i64 = 52 }, INT_MIN, INT_MAX, VE, "level" },
+
+    { NULL },
+};
+
+static const AVClass h264_videotoolbox_class = {
+    .class_name = "h264_videotoolbox",
+    .item_name  = av_default_item_name,
+    .option     = options,
+    .version    = LIBAVUTIL_VERSION_INT,
+};
+
+AVCodec ff_h264_videotoolbox_encoder = {
+    .name             = "h264_videotoolbox",
+    .long_name        = NULL_IF_CONFIG_SMALL("VideoToolbox H.264 Encoder"),
+    .type             = AVMEDIA_TYPE_VIDEO,
+    .id               = AV_CODEC_ID_H264,
+    .priv_data_size   = sizeof(VTEncContext),
+    .pix_fmts         = pix_fmts,
+    .init             = vtenc_init,
+    .encode2          = vtenc_frame,
+    .close            = vtenc_close,
+    .capabilities     = AV_CODEC_CAP_DELAY,
+    .priv_class       = &h264_videotoolbox_class,
+    .caps_internal    = FF_CODEC_CAP_INIT_THREADSAFE |
+                        FF_CODEC_CAP_INIT_CLEANUP,
+};