Re: [FFmpeg-devel] [PATCH v2 2/2] avformat/flvenc: add option to read metadata from file

[Gyan Doshi <ffmpeg@gyani.pro>]

On 2023-02-03 09:04 pm, Andreas Rheinhardt wrote:
> Gyan Doshi:
>> Useful, in conjuntion with option meta_period, to vary metadata during
>> stream.
>>
>> File format is ffmetadata.
>> ---
>>   configure            |   2 +-
>>   doc/muxers.texi      |   3 +
>>   libavformat/flvenc.c | 133 +++++++++++++++++++++++++++++++++----------
>>   3 files changed, 107 insertions(+), 31 deletions(-)
>>
>> diff --git a/configure b/configure
>> index 9d78a244a3..de371632c4 100755
>> --- a/configure
>> +++ b/configure
>> @@ -3433,7 +3433,7 @@ eac3_demuxer_select="ac3_parser"
>>   f4v_muxer_select="mov_muxer"
>>   fifo_muxer_deps="threads"
>>   flac_demuxer_select="flac_parser"
>> -flv_muxer_select="aac_adtstoasc_bsf"
>> +flv_muxer_select="aac_adtstoasc_bsf ffmetadata_demuxer"
>>   gxf_muxer_select="pcm_rechunk_bsf"
>>   hds_muxer_select="flv_muxer"
>>   hls_demuxer_select="adts_header ac3_parser"
>> diff --git a/doc/muxers.texi b/doc/muxers.texi
>> index 02ecddf186..000c92b2a7 100644
>> --- a/doc/muxers.texi
>> +++ b/doc/muxers.texi
>> @@ -555,6 +555,9 @@ With every video packet.
>>   @end table
>>   Note that metadata will always be re-emitted if a metadata update event is signalled.
>>   
>> +@item meta_filename
>> +Specify a ffmetadata file from which to load metadata.
>> +
>>   @end table
>>   
>>   @anchor{framecrc}
>> diff --git a/libavformat/flvenc.c b/libavformat/flvenc.c
>> index d1c7a493d1..1332b18b41 100644
>> --- a/libavformat/flvenc.c
>> +++ b/libavformat/flvenc.c
>> @@ -122,6 +122,10 @@ typedef struct FLVContext {
>>       double framerate;
>>       AVCodecParameters *data_par;
>>   
>> +    char *meta_filename;
>> +    AVFormatContext *meta_ctx;
>> +    AVDictionary *meta_dict;
>> +
>>       int flags;
>>       int meta_period;
>>   } FLVContext;
>> @@ -277,6 +281,92 @@ static void put_amf_bool(AVIOContext *pb, int b)
>>       avio_w8(pb, !!b);
>>   }
>>   
>> +static int read_metadata_from_file(AVFormatContext *s, unsigned int ts, int header)
>> +{
>> +    FLVContext *flv = s->priv_data;
>> +    const AVInputFormat *meta_format = NULL;
>> +    AVDictionary *current_meta_dict = NULL;
>> +    float timestamp = ts/1000.f;
>> +    int ret;
>> +
>> +    if (!flv->meta_filename)
>> +        return 0;
>> +
>> +    meta_format = av_find_input_format("ffmetadata");
>> +    if (!meta_format) {
>> +        av_log(s, AV_LOG_ERROR, "ffmetadata demuxer not found.\n");
>> +        return AVERROR(ENOSYS);
>> +    }
>> +
>> +    avformat_close_input(&flv->meta_ctx);
>> +
>> +    ret = avformat_open_input(&flv->meta_ctx, flv->meta_filename, meta_format, NULL);
>> +    if (ret < 0) {
>> +        av_log(s, AV_LOG_ERROR, "Failed to read metadata from file %s t: %f.", flv->meta_filename, timestamp);
>> +        if (flv->meta_dict)
>> +            av_log(s, AV_LOG_ERROR, " Continuing with old metadata.");
>> +        av_log(s, AV_LOG_ERROR, "\n");
>> +        return ret;
>> +    }
>> +
>> +    if (flv->meta_dict) {
>> +        av_dict_copy(&current_meta_dict, flv->meta_dict, 0);
>> +        av_dict_free(&flv->meta_dict);
>> +    }
>> +
>> +    ret = av_dict_copy(&flv->meta_dict, flv->meta_ctx->metadata, 0);
>> +    if (ret < 0) {
>> +        av_log(s, AV_LOG_ERROR, "Could not transfer metadata from %s at %f seconds. Continuing with old metadata.\n", flv->meta_filename, timestamp);
>> +        av_dict_free(&flv->meta_dict);
>> +        av_dict_copy(&flv->meta_dict, current_meta_dict, 0);
>> +        av_dict_free(&current_meta_dict);
>> +        return ret;
>> +    }
>> +
>> +    av_log(s, AV_LOG_VERBOSE, "Metadata from file %s updated %s at %f seconds.\n", flv->meta_filename, header ? "in header" : "in video packet", timestamp);
>> +    av_dict_free(&current_meta_dict);
>> +    avformat_close_input(&flv->meta_ctx);
>> +
>> +    return 0;
>> +}
>> +
>> +static int write_user_metadata_tag(AVFormatContext *s, AVDictionaryEntry *tag, AVIOContext *pb, int *metadata_count)
>> +{
>> +
>> +    av_log(s, AV_LOG_DEBUG, "Writing tag %s with value %s count: %d\n", tag->key, tag->value, *metadata_count);
>> +
>> +    if(   !strcmp(tag->key, "width")
>> +        ||!strcmp(tag->key, "height")
>> +        ||!strcmp(tag->key, "videodatarate")
>> +        ||!strcmp(tag->key, "framerate")
>> +        ||!strcmp(tag->key, "videocodecid")
>> +        ||!strcmp(tag->key, "audiodatarate")
>> +        ||!strcmp(tag->key, "audiosamplerate")
>> +        ||!strcmp(tag->key, "audiosamplesize")
>> +        ||!strcmp(tag->key, "stereo")
>> +        ||!strcmp(tag->key, "audiocodecid")
>> +        ||!strcmp(tag->key, "duration")
>> +        ||!strcmp(tag->key, "onMetaData")
>> +        ||!strcmp(tag->key, "datasize")
>> +        ||!strcmp(tag->key, "lasttimestamp")
>> +        ||!strcmp(tag->key, "totalframes")
>> +        ||!strcmp(tag->key, "hasAudio")
>> +        ||!strcmp(tag->key, "hasVideo")
>> +        ||!strcmp(tag->key, "hasCuePoints")
>> +        ||!strcmp(tag->key, "hasMetadata")
>> +        ||!strcmp(tag->key, "hasKeyframes")
>> +    ){
>> +        av_log(s, AV_LOG_DEBUG, "Ignoring metadata for %s\n", tag->key);
>> +        return AVERROR(EINVAL);
>> +    }
>> +    put_amf_string(pb, tag->key);
>> +    avio_w8(pb, AMF_DATA_TYPE_STRING);
>> +    put_amf_string(pb, tag->value);
>> +    (*metadata_count)++;
>> +
>> +    return 0;
>> +}
>> +
>>   static void write_metadata(AVFormatContext *s, unsigned int ts)
>>   {
>>       AVIOContext *pb = s->pb;
>> @@ -360,36 +450,11 @@ static void write_metadata(AVFormatContext *s, unsigned int ts)
>>       }
>>   
>>       ff_standardize_creation_time(s);
>> -    while ((tag = av_dict_iterate(s->metadata, tag))) {
>> -        if(   !strcmp(tag->key, "width")
>> -            ||!strcmp(tag->key, "height")
>> -            ||!strcmp(tag->key, "videodatarate")
>> -            ||!strcmp(tag->key, "framerate")
>> -            ||!strcmp(tag->key, "videocodecid")
>> -            ||!strcmp(tag->key, "audiodatarate")
>> -            ||!strcmp(tag->key, "audiosamplerate")
>> -            ||!strcmp(tag->key, "audiosamplesize")
>> -            ||!strcmp(tag->key, "stereo")
>> -            ||!strcmp(tag->key, "audiocodecid")
>> -            ||!strcmp(tag->key, "duration")
>> -            ||!strcmp(tag->key, "onMetaData")
>> -            ||!strcmp(tag->key, "datasize")
>> -            ||!strcmp(tag->key, "lasttimestamp")
>> -            ||!strcmp(tag->key, "totalframes")
>> -            ||!strcmp(tag->key, "hasAudio")
>> -            ||!strcmp(tag->key, "hasVideo")
>> -            ||!strcmp(tag->key, "hasCuePoints")
>> -            ||!strcmp(tag->key, "hasMetadata")
>> -            ||!strcmp(tag->key, "hasKeyframes")
>> -        ){
>> -            av_log(s, AV_LOG_DEBUG, "Ignoring metadata for %s\n", tag->key);
>> -            continue;
>> -        }
>> -        put_amf_string(pb, tag->key);
>> -        avio_w8(pb, AMF_DATA_TYPE_STRING);
>> -        put_amf_string(pb, tag->value);
>> -        metadata_count++;
>> -    }
>> +
>> +    while (tag = av_dict_get(s->metadata, "", tag, AV_DICT_IGNORE_SUFFIX))
>> +        write_user_metadata_tag(s, tag, pb, &metadata_count);
>> +    while (tag = av_dict_get(flv->meta_dict, "", tag, AV_DICT_IGNORE_SUFFIX))
>> +        write_user_metadata_tag(s, tag, pb, &metadata_count);
>>   
>>       if (write_duration_filesize) {
>>           put_amf_string(pb, "filesize");
>> @@ -718,6 +783,7 @@ static int flv_write_header(AVFormatContext *s)
>>       if (flv->flags & FLV_NO_METADATA) {
>>           pb->seekable = 0;
>>       } else {
>> +        read_metadata_from_file(s, 0, 1);
>>           write_metadata(s, 0);
>>       }
>>   
>> @@ -880,6 +946,7 @@ static int flv_write_packet(AVFormatContext *s, AVPacket *pkt)
>>       if (meta_upd_flag ||
>>           (flv->meta_period == FLV_META_AT_KF        && par->codec_type == AVMEDIA_TYPE_VIDEO && (pkt->flags & AV_PKT_FLAG_KEY)) ||
>>           (flv->meta_period == FLV_META_EVERY_PACKET && par->codec_type == AVMEDIA_TYPE_VIDEO )) {
>> +        read_metadata_from_file(s, ts, 0);
>>           write_metadata(s, ts);
>>           if (meta_upd_flag)
>>               s->event_flags &= ~AVSTREAM_EVENT_FLAG_METADATA_UPDATED;
>> @@ -1053,6 +1120,11 @@ static void flv_deinit(AVFormatContext *s)
>>       }
>>       flv->filepositions = flv->head_filepositions = NULL;
>>       flv->filepositions_count = 0;
>> +
>> +    if (flv->meta_dict)
>> +        av_dict_free(&flv->meta_dict);
>> +
>> +    avformat_close_input(&flv->meta_ctx);
>>   }
>>   
>>   static const AVOption options[] = {
>> @@ -1066,6 +1138,7 @@ static const AVOption options[] = {
>>       { "at_start",      "only once at start",        0, AV_OPT_TYPE_CONST, {.i64 = FLV_META_ONCE_AT_START}, INT_MIN, INT_MAX, AV_OPT_FLAG_ENCODING_PARAM, "meta_period" },
>>       { "at_keyframes",  "with every video keyframe", 0, AV_OPT_TYPE_CONST, {.i64 = FLV_META_AT_KF},         INT_MIN, INT_MAX, AV_OPT_FLAG_ENCODING_PARAM, "meta_period" },
>>       { "every_packet",  "with every video packet",   0, AV_OPT_TYPE_CONST, {.i64 = FLV_META_EVERY_PACKET},  INT_MIN, INT_MAX, AV_OPT_FLAG_ENCODING_PARAM, "meta_period" },
>> +    { "meta_filename", "ffmetadata file to import metadata", offsetof(FLVContext, meta_filename), AV_OPT_TYPE_STRING, {.str = NULL},  0, 0, AV_OPT_FLAG_ENCODING_PARAM },
>>       { NULL },
>>   };
>>   
> What does this achieve that can't be achieved by other means (namely by
> an API-user updating the relevant metadata dictionaries)?

This option together with meta_period is for CLI users. Similar to 
drawtext's textfile + reload.
It's been used in production for over a year at a client. Think it will 
be broadly useful.

Regards,
Gyan

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