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

Sat, 04 Feb 2023 02:11:39 -0800 



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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