avformat/matroskaenc: Improve log messages for blocks

Up until now, a block's relative offset has been reported as the offset
in the log messages output when writing blocks; given that it is
impossible to know the real offset from the beginning of the file at
this point due to the fact that it is not yet known how many bytes will
be used for the containing cluster's length field both the relative
offset in the cluster as well as the offset of the containing cluster
will be reported from now on.

Furthermore, the TrackNumber of the written block has been added to the
log output.

Also, the log message for writing vtt blocks has been brought in line
with the message for normal blocks.
Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@gmail.com>
Signed-off-by: James Almer <jamrial@gmail.com>

libavformat/matroskaenc.c

@@ -2124,10 +2124,14 @@ static void mkv_write_block(AVFormatContext *s, AVIOContext *pb,
 
     ts += mkv->tracks[pkt->stream_index].ts_offset;
 
-    av_log(s, AV_LOG_DEBUG, "Writing block at offset %" PRIu64 ", size %d, "
-           "pts %" PRId64 ", dts %" PRId64 ", duration %" PRId64 ", keyframe %d\n",
-           avio_tell(pb), pkt->size, pkt->pts, pkt->dts, pkt->duration,
-           keyframe != 0);
+    /* The following string is identical to the one in mkv_write_vtt_blocks
+     * so that only one copy needs to exist in binaries. */
+    av_log(s, AV_LOG_DEBUG,
+           "Writing block of size %d with pts %" PRId64 ", dts %" PRId64 ", "
+           "duration %" PRId64 " at relative offset %" PRId64 " in cluster "
+           "at offset %" PRId64 ". TrackNumber %d, keyframe %d\n",
+           pkt->size, pkt->pts, pkt->dts, pkt->duration, avio_tell(pb),
+           mkv->cluster_pos, track_number, keyframe != 0);
     if (par->codec_id == AV_CODEC_ID_H264 && par->extradata_size > 0 &&
         (AV_RB24(par->extradata) == 1 || AV_RB32(par->extradata) == 1))
         ff_avc_parse_nal_units_buf(pkt->data, &data, &size);
@@ -2231,9 +2235,14 @@ static int mkv_write_vtt_blocks(AVFormatContext *s, AVIOContext *pb, AVPacket *p
 
     size = id_size + 1 + settings_size + 1 + pkt->size;
 
-    av_log(s, AV_LOG_DEBUG, "Writing block at offset %" PRIu64 ", size %d, "
-           "pts %" PRId64 ", dts %" PRId64 ", duration %" PRId64 ", flags %d\n",
-           avio_tell(pb), size, pkt->pts, pkt->dts, pkt->duration, flags);
+    /* The following string is identical to the one in mkv_write_block so that
+     * only one copy needs to exist in binaries. */
+    av_log(s, AV_LOG_DEBUG,
+           "Writing block of size %d with pts %" PRId64 ", dts %" PRId64 ", "
+           "duration %" PRId64 " at relative offset %" PRId64 " in cluster "
+           "at offset %" PRId64 ". TrackNumber %d, keyframe %d\n",
+           size, pkt->pts, pkt->dts, pkt->duration, avio_tell(pb),
+           mkv->cluster_pos, pkt->stream_index + 1, 1);
 
     blockgroup = start_ebml_master(pb, MATROSKA_ID_BLOCKGROUP, mkv_blockgroup_size(size));