From: ulmus-scott <scott.the....@gmail.com> The flag identifies two independant mono channels recorded as stereo.
This change has been kicking around in the MythTV modifications since 2006. See https://github.com/MythTV/mythtv/commit/435540c9e8ac245ceca968791c67431f37c8d617 I have changed the names and comment. For the current MythTV modification see https://github.com/ulmus-scott/FFmpeg/commit/645fa6f9a61d23bac0665851d211bbeb3686deb0 --- libavcodec/audiotoolboxdec.c | 2 +- libavcodec/avcodec.h | 11 +++++++++++ libavcodec/mpegaudio_parser.c | 2 +- libavcodec/mpegaudiodecheader.c | 4 +++- libavcodec/mpegaudiodecheader.h | 2 +- 5 files changed, 17 insertions(+), 4 deletions(-) diff --git a/libavcodec/audiotoolboxdec.c b/libavcodec/audiotoolboxdec.c index 82babe3d31..9d11844142 100644 --- a/libavcodec/audiotoolboxdec.c +++ b/libavcodec/audiotoolboxdec.c @@ -346,7 +346,7 @@ static av_cold int ffat_create_decoder(AVCodecContext *avctx, int bit_rate; if (ff_mpa_decode_header(AV_RB32(pkt->data), &avctx->sample_rate, &in_format.mChannelsPerFrame, &avctx->frame_size, - &bit_rate, &codec_id) < 0) + &bit_rate, &codec_id, &avctx->mpeg_audio_mode_dual_channel) < 0) return AVERROR_INVALIDDATA; avctx->bit_rate = bit_rate; in_format.mSampleRate = avctx->sample_rate; diff --git a/libavcodec/avcodec.h b/libavcodec/avcodec.h index 7db5d1b1c5..bcf3a845a8 100644 --- a/libavcodec/avcodec.h +++ b/libavcodec/avcodec.h @@ -2076,6 +2076,17 @@ typedef struct AVCodecContext { * The decoder can then override during decoding as needed. */ AVChannelLayout ch_layout; + + /** + * Audio only. This flag is set when MPEG audio mode dual channel has been detected. + * This signals that the audio is two independent mono channels. + * + * 0 normally, 1 if dual channel flag is set. + * + * - encoding: currently unused (functionally equivalent to stereo, patch welcome) + * - decoding: set by lavc + */ + int mpeg_audio_mode_dual_channel; } AVCodecContext; /** diff --git a/libavcodec/mpegaudio_parser.c b/libavcodec/mpegaudio_parser.c index d54366f10a..d957cf467f 100644 --- a/libavcodec/mpegaudio_parser.c +++ b/libavcodec/mpegaudio_parser.c @@ -70,7 +70,7 @@ static int mpegaudio_parse(AVCodecParserContext *s1, state= (state<<8) + buf[i++]; - ret = ff_mpa_decode_header(state, &sr, &channels, &frame_size, &bit_rate, &codec_id); + ret = ff_mpa_decode_header(state, &sr, &channels, &frame_size, &bit_rate, &codec_id, &avctx->mpeg_audio_mode_dual_channel); if (ret < 4) { if (i > 4) s->header_count = -2; diff --git a/libavcodec/mpegaudiodecheader.c b/libavcodec/mpegaudiodecheader.c index ef63befbf4..6c9a641906 100644 --- a/libavcodec/mpegaudiodecheader.c +++ b/libavcodec/mpegaudiodecheader.c @@ -117,7 +117,7 @@ int avpriv_mpegaudio_decode_header(MPADecodeHeader *s, uint32_t header) return 0; } -int ff_mpa_decode_header(uint32_t head, int *sample_rate, int *channels, int *frame_size, int *bit_rate, enum AVCodecID *codec_id) +int ff_mpa_decode_header(uint32_t head, int *sample_rate, int *channels, int *frame_size, int *bit_rate, enum AVCodecID *codec_id, int *dual_mono) { MPADecodeHeader s1, *s = &s1; @@ -148,5 +148,7 @@ int ff_mpa_decode_header(uint32_t head, int *sample_rate, int *channels, int *fr *sample_rate = s->sample_rate; *channels = s->nb_channels; *bit_rate = s->bit_rate; + *dual_mono = (s->mode == MPA_DUAL) ? 1 : 0; + return s->frame_size; } diff --git a/libavcodec/mpegaudiodecheader.h b/libavcodec/mpegaudiodecheader.h index ed5d1f3b33..e599d287f7 100644 --- a/libavcodec/mpegaudiodecheader.h +++ b/libavcodec/mpegaudiodecheader.h @@ -56,7 +56,7 @@ int avpriv_mpegaudio_decode_header(MPADecodeHeader *s, uint32_t header); /* useful helper to get MPEG audio stream info. Return -1 if error in header, otherwise the coded frame size in bytes */ int ff_mpa_decode_header(uint32_t head, int *sample_rate, - int *channels, int *frame_size, int *bitrate, enum AVCodecID *codec_id); + int *channels, int *frame_size, int *bitrate, enum AVCodecID *codec_id, int *dual_mono); /* fast header check for resync */ static inline int ff_mpa_check_header(uint32_t header){ -- 2.34.1 _______________________________________________ ffmpeg-devel mailing list ffmpeg-devel@ffmpeg.org https://ffmpeg.org/mailman/listinfo/ffmpeg-devel To unsubscribe, visit link above, or email ffmpeg-devel-requ...@ffmpeg.org with subject "unsubscribe".
