On Thu, 6 Feb 2014 13:03:44 +0000 Derek Buitenhuis <derek.buitenhuis@gmail.com> wrote:

We are not technically allowed to reuse the codec context found inside the AVStream in the format context.

Signed-off-by: Derek Buitenhuis <derek.buitenhuis@gmail.com> --- doc/examples/demuxing_decoding.c | 37 ++++++++++++++++++++++++++----------- 1 file changed, 26 insertions(+), 11 deletions(-)

diff --git a/doc/examples/demuxing_decoding.c b/doc/examples/demuxing_decoding.c index 0ef5df7..c69e07b 100644 --- a/doc/examples/demuxing_decoding.c +++ b/doc/examples/demuxing_decoding.c @@ -135,12 +135,11 @@ static int decode_packet(int *got_frame, int cached) return decoded; }

-static int open_codec_context(int *stream_idx, - AVFormatContext *fmt_ctx, enum AVMediaType type) +static int open_codec_context(int *stream_idx, AVFormatContext *fmt_ctx, + enum AVMediaType type, AVCodecContext **dec_ctx) { int ret; AVStream *st; - AVCodecContext *dec_ctx = NULL; AVCodec *dec = NULL; AVDictionary *opts = NULL;

@@ -153,19 +152,37 @@ static int open_codec_context(int *stream_idx, *stream_idx = ret; st = fmt_ctx->streams[*stream_idx];

- /* find decoder for the stream */ - dec_ctx = st->codec; - dec = avcodec_find_decoder(dec_ctx->codec_id); + /* find decoder for the stream as a sanity check */ + dec = avcodec_find_decoder(st->codec->codec_id); if (!dec) { fprintf(stderr, "Failed to find %s codec\n", av_get_media_type_string(type)); return AVERROR(EINVAL); }

What exactly does this sanity check? What happens if this code is removed, and there's no codec? Shouldn't one of the functions below simply fail?

+ /* + * Allocate our decoding context, since we are not allowed + * to reuse the one from the AVStream + */ + *dec_ctx = avcodec_alloc_context3(NULL); + if (!*dec_ctx) { + fprintf(stderr, "Failed to allocate %s codec context.\n", + av_get_media_type_string(type)); + return AVERROR(ENOMEM); + } + + /* Copy the properties over */ + ret = avcodec_copy_context(*dec_ctx, st->codec); + if (ret < 0) { + fprintf(stderr, "Failed to copy %s codec context.\n", + av_get_media_type_string(type)); + return AVERROR(EINVAL); + } + /* Init the decoders, with or without reference counting */ if (api_mode == API_MODE_NEW_API_REF_COUNT) av_dict_set(&opts, "refcounted_frames", "1", 0); - if ((ret = avcodec_open2(dec_ctx, dec, &opts)) < 0) { + if ((ret = avcodec_open2(*dec_ctx, dec, &opts)) < 0) { fprintf(stderr, "Failed to open %s codec\n", av_get_media_type_string(type)); return ret; @@ -252,9 +269,8 @@ int main (int argc, char **argv) exit(1); }

- if (open_codec_context(&video_stream_idx, fmt_ctx, AVMEDIA_TYPE_VIDEO) >= 0) { + if (open_codec_context(&video_stream_idx, fmt_ctx, AVMEDIA_TYPE_VIDEO, &video_dec_ctx) >= 0) { video_stream = fmt_ctx->streams[video_stream_idx]; - video_dec_ctx = video_stream->codec;

video_dst_file = fopen(video_dst_filename, "wb"); if (!video_dst_file) { @@ -274,9 +290,8 @@ int main (int argc, char **argv) video_dst_bufsize = ret; }

- if (open_codec_context(&audio_stream_idx, fmt_ctx, AVMEDIA_TYPE_AUDIO) >= 0) { + if (open_codec_context(&audio_stream_idx, fmt_ctx, AVMEDIA_TYPE_AUDIO, &audio_dec_ctx) >= 0) { audio_stream = fmt_ctx->streams[audio_stream_idx]; - audio_dec_ctx = audio_stream->codec; audio_dst_file = fopen(audio_dst_filename, "wb"); if (!audio_dst_file) { fprintf(stderr, "Could not open destination file %s\n", video_dst_filename);