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

[Paul B Mahol <onemda@gmail.com>]

On 2/4/23, Gyan Doshi <ffmpeg@gyani.pro> wrote:
>
>
> 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.

Not everything that is useful now is correct on long term.

Muxer specific metadata handling by reading from files is big hack.

NAK.

>
> Regards,
> Gyan
>
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