On 6/16/20 6:02 PM, Przemysław Sobala wrote:
> If stream's bitrate is not specified:
> - for static manifest: an average bitrate will be calculated and used,
> - for dynamic manifest: first segment's bitrate will be calculated and used,
> as before,
> for bandwidth setting in adaptation sets.
>
> For dynamic manifest
> ---
> libavformat/dashenc.c | 28 +++++++++++++++++++++-------
> 1 file changed, 21 insertions(+), 7 deletions(-)
>
> diff --git a/libavformat/dashenc.c b/libavformat/dashenc.c
> index 05deb5c1b5..6e1a6dbf3a 100644
> --- a/libavformat/dashenc.c
> +++ b/libavformat/dashenc.c
> @@ -115,6 +115,8 @@ typedef struct OutputStream {
> int64_t last_dts, last_pts;
> int last_flags;
> int bit_rate;
> + int first_segment_bit_rate;
> + double average_bit_rate;
> SegmentType segment_type; /* segment type selected for this particular
> stream */
> const char *format_name;
> const char *extension_name;
> @@ -840,8 +842,11 @@ static int write_adaptation_set(AVFormatContext *s,
> AVIOContext *out, int as_ind
> continue;
>
> if (os->bit_rate > 0)
> - snprintf(bandwidth_str, sizeof(bandwidth_str), "
> bandwidth=\"%d\"",
> - os->bit_rate);
> + snprintf(bandwidth_str, sizeof(bandwidth_str), "
> bandwidth=\"%d\"", os->bit_rate);
> + else if (final && os->average_bit_rate > 0)
> + snprintf(bandwidth_str, sizeof(bandwidth_str), "
> bandwidth=\"%d\"", (int) os->average_bit_rate);
> + else if (os->first_segment_bit_rate > 0)
> + snprintf(bandwidth_str, sizeof(bandwidth_str), "
> bandwidth=\"%d\"", os->first_segment_bit_rate);
>
> if (as->media_type == AVMEDIA_TYPE_VIDEO) {
> avio_printf(out, "\t\t\t<Representation id=\"%d\"
> mimeType=\"video/%s\" codecs=\"%s\"%s width=\"%d\" height=\"%d\"",
> @@ -1305,7 +1310,13 @@ static int write_manifest(AVFormatContext *s, int
> final)
> OutputStream *os = &c->streams[i];
> char *agroup = NULL;
> char *codec_str_ptr = NULL;
> - int stream_bitrate = st->codecpar->bit_rate + os->muxer_overhead;
> + int stream_bitrate = os->muxer_overhead;
> + if (os->bit_rate > 0)
> + stream_bitrate += os->bit_rate;
> + else if (final && os->average_bit_rate > 0)
> + stream_bitrate += os->average_bit_rate;
> + else if (os->first_segment_bit_rate > 0)
> + stream_bitrate += os->first_segment_bit_rate;
> if (st->codecpar->codec_type != AVMEDIA_TYPE_VIDEO)
> continue;
> if (os->segment_type != SEGMENT_TYPE_MP4)
> @@ -1959,10 +1970,13 @@ static int dash_flush(AVFormatContext *s, int final,
> int stream)
> os->total_pkt_duration = 0;
>
> if (!os->bit_rate) {
> - // calculate average bitrate of first segment
> - int64_t bitrate = (int64_t) range_length * 8 * AV_TIME_BASE /
> duration;
> - if (bitrate >= 0)
> - os->bit_rate = bitrate;
> + // calculate average bitrate
> + int64_t segment_bitrate = (int64_t) range_length * 8 *
> AV_TIME_BASE / duration;
> + if (!os->first_segment_bit_rate)
> + os->first_segment_bit_rate = segment_bitrate;
> + os->average_bit_rate = (os->average_bit_rate *
> (os->segment_index - 1) + segment_bitrate) / os->segment_index;
This method of calculating average bitrate may not be accurate in all cases.
Could you just add all "range_length" values and divide it total duration
finally to get the average bitrate value.
Otherwise, the overall idea LGTM.
> + av_log(s, AV_LOG_INFO, "segment_bitrate: %"PRId64",
> os->first_segment_bit_rate: %i, os->average_bit_rate: %f\n",
> + segment_bitrate, os->first_segment_bit_rate,
> os->average_bit_rate);
> }
> add_segment(os, os->filename, os->start_pts, os->max_pts -
> os->start_pts, os->pos, range_length, index_length, next_exp_index);
> av_log(s, AV_LOG_VERBOSE, "Representation %d media segment %d
> written to: %s\n", i, os->segment_index, os->full_path);
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