From 0224b35c89e9e75f156962c93b37adab75d8df6a Mon Sep 17 00:00:00 2001 From: Andreas Cadhalpun Date: Fri, 3 Apr 2015 18:19:53 +0200 Subject: avcodec: add unpack packed B-frames bitstream filter Fixes Ticket #2913 Signed-off-by: Andreas Cadhalpun Signed-off-by: Michael Niedermayer --- libavcodec/mpeg4_unpack_bframes_bsf.c | 194 ++++++++++++++++++++++++++++++++++ 1 file changed, 194 insertions(+) create mode 100644 libavcodec/mpeg4_unpack_bframes_bsf.c (limited to 'libavcodec/mpeg4_unpack_bframes_bsf.c') diff --git a/libavcodec/mpeg4_unpack_bframes_bsf.c b/libavcodec/mpeg4_unpack_bframes_bsf.c new file mode 100644 index 0000000000..e85ea08b08 --- /dev/null +++ b/libavcodec/mpeg4_unpack_bframes_bsf.c @@ -0,0 +1,194 @@ +/* + * Bitstream filter for unpacking DivX-style packed B-frames in MPEG-4 (divx_packed) + * Copyright (c) 2015 Andreas Cadhalpun + * + * 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 "avcodec.h" +#include "mpeg4video.h" + +typedef struct UnpackBFramesBSFContext { + uint8_t *b_frame_buf; + int b_frame_buf_size; + int updated_extradata; +} UnpackBFramesBSFContext; + +/* search next start code */ +static unsigned int find_startcode(const uint8_t *buf, int buf_size, int *pos) +{ + unsigned int startcode = 0xFF; + + for (; *pos < buf_size;) { + startcode = ((startcode << 8) | buf[*pos]) & 0xFFFFFFFF; + *pos +=1; + if ((startcode & 0xFFFFFF00) != 0x100) + continue; /* no startcode */ + return startcode; + } + + return 0; +} + +/* determine the position of the packed marker in the userdata, + * the number of VOPs and the position of the second VOP */ +static void scan_buffer(const uint8_t *buf, int buf_size, + int *pos_p, int *nb_vop, int *pos_vop2) { + unsigned int startcode; + int pos, i; + + for (pos = 0; pos < buf_size;) { + startcode = find_startcode(buf, buf_size, &pos); + + if (startcode == USER_DATA_STARTCODE && pos_p) { + /* check if the (DivX) userdata string ends with 'p' (packed) */ + for (i = 0; i < 255 && pos + i + 1 < buf_size; i++) { + if (buf[pos + i] == 'p' && buf[pos + i + 1] == '\0') { + *pos_p = pos + i; + break; + } + } + } else if (startcode == VOP_STARTCODE && nb_vop) { + *nb_vop += 1; + if (*nb_vop == 2 && pos_vop2) { + *pos_vop2 = pos - 4; /* subtract 4 bytes startcode */ + } + } + } +} + +/* allocate new buffer and copy size bytes from src */ +static uint8_t *create_new_buffer(const uint8_t *src, int size) { + uint8_t *dst = av_malloc(size + FF_INPUT_BUFFER_PADDING_SIZE); + + if (dst) { + memcpy(dst, src, size); + memset(dst + size, 0, FF_INPUT_BUFFER_PADDING_SIZE); + } + + return dst; +} + +static int mpeg4_unpack_bframes_filter(AVBitStreamFilterContext *bsfc, + AVCodecContext *avctx, const char *args, + uint8_t **poutbuf, int *poutbuf_size, + const uint8_t *buf, int buf_size, + int keyframe) +{ + UnpackBFramesBSFContext *ctx = bsfc->priv_data; + int pos_p = -1, nb_vop = 0, pos_vop2 = -1, ret = 0; + + if (avctx->codec_id != AV_CODEC_ID_MPEG4) { + av_log(avctx, AV_LOG_ERROR, + "The mpeg4_unpack_bframes bitstream filter is only useful for mpeg4.\n"); + return AVERROR(EINVAL); + } + + if (!ctx->updated_extradata && avctx->extradata) { + int pos_p_ext = -1; + scan_buffer(avctx->extradata, avctx->extradata_size, &pos_p_ext, NULL, NULL); + if (pos_p_ext >= 0) { + av_log(avctx, AV_LOG_DEBUG, + "Updating DivX userdata (remove trailing 'p') in extradata.\n"); + avctx->extradata[pos_p_ext] = '\0'; + } + ctx->updated_extradata = 1; + } + + scan_buffer(buf, buf_size, &pos_p, &nb_vop, &pos_vop2); + av_log(avctx, AV_LOG_DEBUG, "Found %d VOP startcode(s) in this packet.\n", nb_vop); + + if (pos_vop2 >= 0) { + if (ctx->b_frame_buf) { + av_log(avctx, AV_LOG_WARNING, + "Missing one N-VOP packet, discarding one B-frame.\n"); + av_freep(&ctx->b_frame_buf); + ctx->b_frame_buf_size = 0; + } + /* store the packed B-frame in the BSFContext */ + ctx->b_frame_buf_size = buf_size - pos_vop2; + ctx->b_frame_buf = create_new_buffer(buf + pos_vop2, ctx->b_frame_buf_size); + if (!ctx->b_frame_buf) { + ctx->b_frame_buf_size = 0; + return AVERROR(ENOMEM); + } + } + + if (nb_vop > 2) { + av_log(avctx, AV_LOG_WARNING, + "Found %d VOP headers in one packet, only unpacking one.\n", nb_vop); + } + + if (nb_vop == 1 && ctx->b_frame_buf) { + /* use frame from BSFContext */ + *poutbuf = ctx->b_frame_buf; + *poutbuf_size = ctx->b_frame_buf_size; + /* the output buffer is distinct from the input buffer */ + ret = 1; + if (buf_size <= MAX_NVOP_SIZE) { + /* N-VOP */ + av_log(avctx, AV_LOG_DEBUG, "Skipping N-VOP.\n"); + ctx->b_frame_buf = NULL; + ctx->b_frame_buf_size = 0; + } else { + /* copy packet into BSFContext */ + ctx->b_frame_buf_size = buf_size; + ctx->b_frame_buf = create_new_buffer(buf , buf_size); + if (!ctx->b_frame_buf) { + ctx->b_frame_buf_size = 0; + av_freep(poutbuf); + *poutbuf_size = 0; + return AVERROR(ENOMEM); + } + } + } else if (nb_vop >= 2) { + /* use first frame of the packet */ + *poutbuf = (uint8_t *) buf; + *poutbuf_size = pos_vop2; + } else if (pos_p >= 0) { + av_log(avctx, AV_LOG_DEBUG, "Updating DivX userdata (remove trailing 'p').\n"); + *poutbuf_size = buf_size; + *poutbuf = create_new_buffer(buf, buf_size); + if (!*poutbuf) { + *poutbuf_size = 0; + return AVERROR(ENOMEM); + } + /* remove 'p' (packed) from the end of the (DivX) userdata string */ + (*poutbuf)[pos_p] = '\0'; + /* the output buffer is distinct from the input buffer */ + ret = 1; + } else { + /* copy packet */ + *poutbuf = (uint8_t *) buf; + *poutbuf_size = buf_size; + } + + return ret; +} + +static void mpeg4_unpack_bframes_close(AVBitStreamFilterContext *bsfc) +{ + UnpackBFramesBSFContext *ctx = bsfc->priv_data; + av_freep(&ctx->b_frame_buf); +} + +AVBitStreamFilter ff_mpeg4_unpack_bframes_bsf = { + .name = "mpeg4_unpack_bframes", + .priv_data_size = sizeof(UnpackBFramesBSFContext), + .filter = mpeg4_unpack_bframes_filter, + .close = mpeg4_unpack_bframes_close +}; -- cgit v1.2.3