avcodec: add avcodec_get_supported_config()

This replaces the myriad of existing lists in AVCodec by a unified API
call, allowing us to (ultimately) trim down the sizeof(AVCodec) quite
substantially, while also making this more trivially extensible.

In addition to the already covered lists, add two new entries for color
space and color range, mirroring the newly added negotiable fields in
libavfilter.

I decided to drop the explicit length field from the API proposed by
Andreas Rheinhardt, because having it in place ended up complicating
both the codec side and the client side implementations, while also
being strictly less flexible (it's trivial to recover a length given
a terminator, but requires allocation to add a terminator given
a length). Using a terminator also presents less of a porting challenge
for existing users of the current API.

Once the deprecation period passes for the existing public fields, the
rough plan is to move the commonly used fields (such as
pix_fmt/sample_fmt) into FFCodec, possibly as a union of audio and video
configuration types, and then implement the rarely used fields with
custom callbacks.

6 files changed, 148 insertions, 6 deletions

diff --git a/doc/APIchanges b/doc/APIchanges
index 0a39b6d7ab..fdeae67159 100644
--- a/doc/APIchanges
+++ b/doc/APIchanges
@@ -2,6 +2,11 @@ The last version increases of all libraries were on 2024-03-07
 
 API changes, most recent first:
 
+2024-04-xx - xxxxxxxxxx - lavc 59.6.100 - avcodec.h
+  Add avcodec_get_supported_config() and enum AVCodecConfig; deprecate
+  AVCodec.pix_fmts, AVCodec.sample_fmts, AVCodec.supported_framerates,
+  AVCodec.supported_samplerates and AVCodec.ch_layouts.
+
 2024-04-03 - xxxxxxxxxx - lavu 59.13.100 - pixfmt.h
   Add AVCOL_SPC_IPT_C2, AVCOL_SPC_YCGCO_RE and AVCOL_SPC_YCGCO_RO
   to map new matrix coefficients defined by H.273 v3.
diff --git a/libavcodec/avcodec.c b/libavcodec/avcodec.c
index 525fe516bd..96728546d6 100644
--- a/libavcodec/avcodec.c
+++ b/libavcodec/avcodec.c
@@ -700,3 +700,78 @@ int attribute_align_arg avcodec_receive_frame(AVCodecContext *avctx, AVFrame *fr
         return ff_decode_receive_frame(avctx, frame);
     return ff_encode_receive_frame(avctx, frame);
 }
+
+#define WRAP_CONFIG(allowed_type, field)    \
+    do {                                    \
+        if (codec->type != (allowed_type))  \
+            return AVERROR(EINVAL);         \
+        *out_configs = (field);             \
+        return 0;                           \
+    } while (0)
+
+static const enum AVColorRange color_range_jpeg[] = {
+    AVCOL_RANGE_JPEG, AVCOL_RANGE_UNSPECIFIED
+};
+
+static const enum AVColorRange color_range_mpeg[] = {
+    AVCOL_RANGE_MPEG, AVCOL_RANGE_UNSPECIFIED
+};
+
+static const enum AVColorRange color_range_all[] = {
+    AVCOL_RANGE_MPEG, AVCOL_RANGE_JPEG, AVCOL_RANGE_UNSPECIFIED
+};
+
+static const enum AVColorRange *color_range_table[] = {
+    [AVCOL_RANGE_MPEG] = color_range_mpeg,
+    [AVCOL_RANGE_JPEG] = color_range_jpeg,
+    [AVCOL_RANGE_MPEG | AVCOL_RANGE_JPEG] = color_range_all,
+};
+
+int ff_default_get_supported_config(const AVCodecContext *avctx,
+                                    const AVCodec *codec,
+                                    enum AVCodecConfig config,
+                                    unsigned flags,
+                                    const void **out_configs)
+{
+    switch (config) {
+FF_DISABLE_DEPRECATION_WARNINGS
+    case AV_CODEC_CONFIG_PIX_FORMAT:
+        WRAP_CONFIG(AVMEDIA_TYPE_VIDEO, codec->pix_fmts);
+    case AV_CODEC_CONFIG_FRAME_RATE:
+        WRAP_CONFIG(AVMEDIA_TYPE_VIDEO, codec->supported_framerates);
+    case AV_CODEC_CONFIG_SAMPLE_RATE:
+        WRAP_CONFIG(AVMEDIA_TYPE_AUDIO, codec->supported_samplerates);
+    case AV_CODEC_CONFIG_SAMPLE_FORMAT:
+        WRAP_CONFIG(AVMEDIA_TYPE_AUDIO, codec->sample_fmts);
+    case AV_CODEC_CONFIG_CHANNEL_LAYOUT:
+        WRAP_CONFIG(AVMEDIA_TYPE_AUDIO, codec->ch_layouts);
+FF_ENABLE_DEPRECATION_WARNINGS
+
+    case AV_CODEC_CONFIG_COLOR_RANGE:
+        if (codec->type != AVMEDIA_TYPE_VIDEO)
+            return AVERROR(EINVAL);
+        *out_configs = color_range_table[ffcodec(codec)->color_ranges];
+        return 0;
+
+    case AV_CODEC_CONFIG_COLOR_SPACE:
+        *out_configs = NULL;
+        return 0;
+    default:
+        return AVERROR(EINVAL);
+    }
+}
+
+int avcodec_get_supported_config(const AVCodecContext *avctx, const AVCodec *codec,
+                                 enum AVCodecConfig config, unsigned flags,
+                                 const void **out)
+{
+    const FFCodec *codec2;
+    if (!codec)
+        codec = avctx->codec;
+    codec2 = ffcodec(codec);
+    if (codec2->get_supported_config) {
+        return codec2->get_supported_config(avctx, codec, config, flags, out);
+    } else {
+        return ff_default_get_supported_config(avctx, codec, config, flags, out);
+    }
+}
diff --git a/libavcodec/avcodec.h b/libavcodec/avcodec.h
index 83dc487251..64f31375fc 100644
--- a/libavcodec/avcodec.h
+++ b/libavcodec/avcodec.h
@@ -2690,6 +2690,33 @@ int avcodec_get_hw_frames_parameters(AVCodecContext *avctx,
                                      enum AVPixelFormat hw_pix_fmt,
                                      AVBufferRef **out_frames_ref);
 
+enum AVCodecConfig {
+    AV_CODEC_CONFIG_PIX_FORMAT,     ///< AVPixelFormat, terminated by AV_PIX_FMT_NONE
+    AV_CODEC_CONFIG_FRAME_RATE,     ///< AVRational, terminated by {0, 0}
+    AV_CODEC_CONFIG_SAMPLE_RATE,    ///< int, terminated by 0
+    AV_CODEC_CONFIG_SAMPLE_FORMAT,  ///< AVSampleFormat, terminated by AV_SAMPLE_FMT_NONE
+    AV_CODEC_CONFIG_CHANNEL_LAYOUT, ///< AVChannelLayout, terminated by {0}
+    AV_CODEC_CONFIG_COLOR_RANGE,    ///< AVColorRange, terminated by AVCOL_RANGE_UNSPECIFIED
+    AV_CODEC_CONFIG_COLOR_SPACE,    ///< AVColorSpace, terminated by AVCOL_SPC_UNSPECIFIED
+};
+
+/**
+ * Retrieve a list of all supported values for a given configuration type.
+ *
+ * @param avctx An optional context to use. Values such as
+ *              `strict_std_compliance` may affect the result. If NULL,
+ *              default values are used.
+ * @param codec The codec to query, or NULL to use avctx->codec.
+ * @param config The configuration to query.
+ * @param flags Currently unused; should be set to zero.
+ * @param out_configs On success, set to a list of configurations, terminated
+ *                    by a config-specific terminator, or NULL if all
+ *                    possible values are supported.
+ */
+int avcodec_get_supported_config(const AVCodecContext *avctx,
+                                 const AVCodec *codec, enum AVCodecConfig config,
+                                 unsigned flags, const void **out_configs);
+
 
 
 /**
diff --git a/libavcodec/codec.h b/libavcodec/codec.h
index 6f9b42760d..f7541ffc42 100644
--- a/libavcodec/codec.h
+++ b/libavcodec/codec.h
@@ -205,10 +205,19 @@ typedef struct AVCodec {
      */
     int capabilities;
     uint8_t max_lowres;                     ///< maximum value for lowres supported by the decoder
-    const AVRational *supported_framerates; ///< array of supported framerates, or NULL if any, array is terminated by {0,0}
-    const enum AVPixelFormat *pix_fmts;     ///< array of supported pixel formats, or NULL if unknown, array is terminated by -1
-    const int *supported_samplerates;       ///< array of supported audio samplerates, or NULL if unknown, array is terminated by 0
-    const enum AVSampleFormat *sample_fmts; ///< array of supported sample formats, or NULL if unknown, array is terminated by -1
+
+    /**
+     * Deprecated codec capabilities.
+     */
+    attribute_deprecated
+    const AVRational *supported_framerates; ///< @deprecated use avcodec_get_supported_config()
+    attribute_deprecated
+    const enum AVPixelFormat *pix_fmts;     ///< @deprecated use avcodec_get_supported_config()
+    attribute_deprecated
+    const int *supported_samplerates;       ///< @deprecated use avcodec_get_supported_config()
+    attribute_deprecated
+    const enum AVSampleFormat *sample_fmts; ///< @deprecated use avcodec_get_supported_config()
+
     const AVClass *priv_class;              ///< AVClass for the private context
     const AVProfile *profiles;              ///< array of recognized profiles, or NULL if unknown, array is terminated by {AV_PROFILE_UNKNOWN}
 
@@ -226,7 +235,9 @@ typedef struct AVCodec {
 
     /**
      * Array of supported channel layouts, terminated with a zeroed layout.
+     * @deprecated use avcodec_get_supported_config()
      */
+    attribute_deprecated
     const AVChannelLayout *ch_layouts;
 } AVCodec;
 
diff --git a/libavcodec/codec_internal.h b/libavcodec/codec_internal.h
index 2134f18409..bac3e30ba2 100644
--- a/libavcodec/codec_internal.h
+++ b/libavcodec/codec_internal.h
@@ -22,6 +22,7 @@
 #include <stdint.h>
 
 #include "libavutil/attributes.h"
+#include "avcodec.h"
 #include "codec.h"
 #include "config.h"
 
@@ -270,8 +271,31 @@ typedef struct FFCodec {
      * List of supported codec_tags, terminated by FF_CODEC_TAGS_END.
      */
     const uint32_t *codec_tags;
+
+    /**
+     * Custom callback for avcodec_get_supported_config(). If absent,
+     * ff_default_get_supported_config() will be used.
+     */
+    int (*get_supported_config)(const AVCodecContext *avctx,
+                                const AVCodec *codec,
+                                enum AVCodecConfig config,
+                                unsigned flags,
+                                const void **out_configs);
 } FFCodec;
 
+/**
+ * Default implementation for avcodec_get_supported_config(). Will return the
+ * relevant fields from AVCodec if present, or NULL otherwise.
+ *
+ * For AVCODEC_CONFIG_COLOR_RANGE, the output will depend on the bitmask in
+ * FFCodec.color_ranges, with a value of 0 returning NULL.
+ */
+int ff_default_get_supported_config(const AVCodecContext *avctx,
+                                    const AVCodec *codec,
+                                    enum AVCodecConfig config,
+                                    unsigned flags,
+                                    const void **out_configs);
+
 #if CONFIG_SMALL
 #define CODEC_LONG_NAME(str) .p.long_name = NULL
 #else
diff --git a/libavcodec/version.h b/libavcodec/version.h
index 84a1c02ce4..da54f87887 100644
--- a/libavcodec/version.h
+++ b/libavcodec/version.h
@@ -29,8 +29,8 @@
 
 #include "version_major.h"
 
-#define LIBAVCODEC_VERSION_MINOR   5
-#define LIBAVCODEC_VERSION_MICRO 101
+#define LIBAVCODEC_VERSION_MINOR   6
+#define LIBAVCODEC_VERSION_MICRO 100
 
 #define LIBAVCODEC_VERSION_INT  AV_VERSION_INT(LIBAVCODEC_VERSION_MAJOR, \
                                                LIBAVCODEC_VERSION_MINOR, \