lavf: replace AVStream.codec with AVStream.codecpar

Currently, AVStream contains an embedded AVCodecContext instance, which
is used by demuxers to export stream parameters to the caller and by
muxers to receive stream parameters from the caller. It is also used
internally as the codec context that is passed to parsers.

In addition, it is also widely used by the callers as the decoding (when
demuxer) or encoding (when muxing) context, though this has been
officially discouraged since Libav 11.

There are multiple important problems with this approach:
    - the fields in AVCodecContext are in general one of
        * stream parameters
        * codec options
        * codec state
      However, it's not clear which ones are which. It is consequently
      unclear which fields are a demuxer allowed to set or a muxer allowed to
      read. This leads to erratic behaviour depending on whether decoding or
      encoding is being performed or not (and whether it uses the AVStream
      embedded codec context).
    - various synchronization issues arising from the fact that the same
      context is used by several different APIs (muxers/demuxers,
      parsers, bitstream filters and encoders/decoders) simultaneously, with
      there being no clear rules for who can modify what and the different
      processes being typically delayed with respect to each other.
    - avformat_find_stream_info() making it necessary to support opening
      and closing a single codec context multiple times, thus
      complicating the semantics of freeing various allocated objects in the
      codec context.

Those problems are resolved by replacing the AVStream embedded codec
context with a newly added AVCodecParameters instance, which stores only
the stream parameters exported by the demuxers or read by the muxers.

1 files changed, 50 insertions, 32 deletions

diff --git a/libavformat/mux.c b/libavformat/mux.c
index ddc69f94a5..76662ee033 100644
--- a/libavformat/mux.c
+++ b/libavformat/mux.c
@@ -67,12 +67,12 @@ static int validate_codec_tag(AVFormatContext *s, AVStream *st)
     for (n = 0; s->oformat->codec_tag[n]; n++) {
         avctag = s->oformat->codec_tag[n];
         while (avctag->id != AV_CODEC_ID_NONE) {
-            if (avpriv_toupper4(avctag->tag) == avpriv_toupper4(st->codec->codec_tag)) {
+            if (avpriv_toupper4(avctag->tag) == avpriv_toupper4(st->codecpar->codec_tag)) {
                 id = avctag->id;
-                if (id == st->codec->codec_id)
+                if (id == st->codecpar->codec_id)
                     return 1;
             }
-            if (avctag->id == st->codec->codec_id)
+            if (avctag->id == st->codecpar->codec_id)
                 tag = avctag->tag;
             avctag++;
         }
@@ -90,7 +90,7 @@ static int init_muxer(AVFormatContext *s, AVDictionary **options)
     int ret = 0, i;
     AVStream *st;
     AVDictionary *tmp = NULL;
-    AVCodecContext *codec = NULL;
+    AVCodecParameters *par = NULL;
     AVOutputFormat *of = s->oformat;
     const AVCodecDescriptor *desc;
 
@@ -101,8 +101,10 @@ static int init_muxer(AVFormatContext *s, AVDictionary **options)
         goto fail;
 
 #if FF_API_LAVF_BITEXACT
+FF_DISABLE_DEPRECATION_WARNINGS
     if (s->nb_streams && s->streams[0]->codec->flags & AV_CODEC_FLAG_BITEXACT)
         s->flags |= AVFMT_FLAG_BITEXACT;
+FF_ENABLE_DEPRECATION_WARNINGS
 #endif
 
     // some sanity checks
@@ -113,41 +115,55 @@ static int init_muxer(AVFormatContext *s, AVDictionary **options)
     }
 
     for (i = 0; i < s->nb_streams; i++) {
-        st    = s->streams[i];
-        codec = st->codec;
+        st  = s->streams[i];
+        par = st->codecpar;
 
 #if FF_API_LAVF_CODEC_TB
 FF_DISABLE_DEPRECATION_WARNINGS
-        if (!st->time_base.num && codec->time_base.num) {
+        if (!st->time_base.num && st->codec->time_base.num) {
             av_log(s, AV_LOG_WARNING, "Using AVStream.codec.time_base as a "
                    "timebase hint to the muxer is deprecated. Set "
                    "AVStream.time_base instead.\n");
-            avpriv_set_pts_info(st, 64, codec->time_base.num, codec->time_base.den);
+            avpriv_set_pts_info(st, 64, st->codec->time_base.num, st->codec->time_base.den);
+        }
+FF_ENABLE_DEPRECATION_WARNINGS
+#endif
+
+#if FF_API_LAVF_AVCTX
+FF_DISABLE_DEPRECATION_WARNINGS
+        if (st->codecpar->codec_type == AVMEDIA_TYPE_UNKNOWN &&
+            st->codec->codec_type    != AVMEDIA_TYPE_UNKNOWN) {
+            av_log(s, AV_LOG_WARNING, "Using AVStream.codec to pass codec "
+                   "parameters to muxers is deprecated, use AVStream.codecpar "
+                   "instead.\n");
+            ret = avcodec_parameters_from_context(st->codecpar, st->codec);
+            if (ret < 0)
+                goto fail;
         }
 FF_ENABLE_DEPRECATION_WARNINGS
 #endif
 
         if (!st->time_base.num) {
             /* fall back on the default timebase values */
-            if (codec->codec_type == AVMEDIA_TYPE_AUDIO && codec->sample_rate)
-                avpriv_set_pts_info(st, 64, 1, codec->sample_rate);
+            if (par->codec_type == AVMEDIA_TYPE_AUDIO && par->sample_rate)
+                avpriv_set_pts_info(st, 64, 1, par->sample_rate);
             else
                 avpriv_set_pts_info(st, 33, 1, 90000);
         }
 
-        switch (codec->codec_type) {
+        switch (par->codec_type) {
         case AVMEDIA_TYPE_AUDIO:
-            if (codec->sample_rate <= 0) {
+            if (par->sample_rate <= 0) {
                 av_log(s, AV_LOG_ERROR, "sample rate not set\n");
                 ret = AVERROR(EINVAL);
                 goto fail;
             }
-            if (!codec->block_align)
-                codec->block_align = codec->channels *
-                                     av_get_bits_per_sample(codec->codec_id) >> 3;
+            if (!par->block_align)
+                par->block_align = par->channels *
+                                   av_get_bits_per_sample(par->codec_id) >> 3;
             break;
         case AVMEDIA_TYPE_VIDEO:
-            if ((codec->width <= 0 || codec->height <= 0) &&
+            if ((par->width <= 0 || par->height <= 0) &&
                 !(of->flags & AVFMT_NODIMENSIONS)) {
                 av_log(s, AV_LOG_ERROR, "dimensions not set\n");
                 ret = AVERROR(EINVAL);
@@ -155,16 +171,16 @@ FF_ENABLE_DEPRECATION_WARNINGS
             }
 
             if (av_cmp_q(st->sample_aspect_ratio,
-                         codec->sample_aspect_ratio)) {
+                         par->sample_aspect_ratio)) {
                 if (st->sample_aspect_ratio.num != 0 &&
                     st->sample_aspect_ratio.den != 0 &&
-                    codec->sample_aspect_ratio.den != 0 &&
-                    codec->sample_aspect_ratio.den != 0) {
+                    par->sample_aspect_ratio.den != 0 &&
+                    par->sample_aspect_ratio.den != 0) {
                     av_log(s, AV_LOG_ERROR, "Aspect ratio mismatch between muxer "
                             "(%d/%d) and encoder layer (%d/%d)\n",
                             st->sample_aspect_ratio.num, st->sample_aspect_ratio.den,
-                            codec->sample_aspect_ratio.num,
-                            codec->sample_aspect_ratio.den);
+                            par->sample_aspect_ratio.num,
+                            par->sample_aspect_ratio.den);
                     ret = AVERROR(EINVAL);
                     goto fail;
                 }
@@ -172,34 +188,34 @@ FF_ENABLE_DEPRECATION_WARNINGS
             break;
         }
 
-        desc = avcodec_descriptor_get(codec->codec_id);
+        desc = avcodec_descriptor_get(par->codec_id);
         if (desc && desc->props & AV_CODEC_PROP_REORDER)
             st->internal->reorder = 1;
 
         if (of->codec_tag) {
-            if (codec->codec_tag &&
-                codec->codec_id == AV_CODEC_ID_RAWVIDEO &&
-                !av_codec_get_tag(of->codec_tag, codec->codec_id) &&
+            if (par->codec_tag &&
+                par->codec_id == AV_CODEC_ID_RAWVIDEO &&
+                !av_codec_get_tag(of->codec_tag, par->codec_id) &&
                 !validate_codec_tag(s, st)) {
                 // the current rawvideo encoding system ends up setting
                 // the wrong codec_tag for avi, we override it here
-                codec->codec_tag = 0;
+                par->codec_tag = 0;
             }
-            if (codec->codec_tag) {
+            if (par->codec_tag) {
                 if (!validate_codec_tag(s, st)) {
                     char tagbuf[32];
-                    av_get_codec_tag_string(tagbuf, sizeof(tagbuf), codec->codec_tag);
+                    av_get_codec_tag_string(tagbuf, sizeof(tagbuf), par->codec_tag);
                     av_log(s, AV_LOG_ERROR,
                            "Tag %s/0x%08x incompatible with output codec id '%d'\n",
-                           tagbuf, codec->codec_tag, codec->codec_id);
+                           tagbuf, par->codec_tag, par->codec_id);
                     ret = AVERROR_INVALIDDATA;
                     goto fail;
                 }
             } else
-                codec->codec_tag = av_codec_get_tag(of->codec_tag, codec->codec_id);
+                par->codec_tag = av_codec_get_tag(of->codec_tag, par->codec_id);
         }
 
-        if (codec->codec_type != AVMEDIA_TYPE_ATTACHMENT)
+        if (par->codec_type != AVMEDIA_TYPE_ATTACHMENT)
             s->internal->nb_interleaved_streams++;
     }
 
@@ -258,6 +274,7 @@ int avformat_write_header(AVFormatContext *s, AVDictionary **options)
 }
 
 #if FF_API_COMPUTE_PKT_FIELDS2
+FF_DISABLE_DEPRECATION_WARNINGS
 //FIXME merge with compute_pkt_fields
 static int compute_pkt_fields2(AVFormatContext *s, AVStream *st, AVPacket *pkt)
 {
@@ -324,6 +341,7 @@ static int compute_pkt_fields2(AVFormatContext *s, AVStream *st, AVPacket *pkt)
 
     return 0;
 }
+FF_ENABLE_DEPRECATION_WARNINGS
 #endif
 
 /*
@@ -384,7 +402,7 @@ static int check_packet(AVFormatContext *s, AVPacket *pkt)
         return AVERROR(EINVAL);
     }
 
-    if (s->streams[pkt->stream_index]->codec->codec_type == AVMEDIA_TYPE_ATTACHMENT) {
+    if (s->streams[pkt->stream_index]->codecpar->codec_type == AVMEDIA_TYPE_ATTACHMENT) {
         av_log(s, AV_LOG_ERROR, "Received a packet for an attachment stream.\n");
         return AVERROR(EINVAL);
     }