[FFmpeg-devel] HLS Questions

Mon May 7 22:52:19 EEST 2018

On Wed, May 2, 2018 at 7:59 AM, Ronak Patel <
ronak2121-at-yahoo.com at ffmpeg.org> wrote:

> Hi all,
>
> So I’ve noticed that ffmpeg does not always properly follow the number we
> specify for hls_time when generating hls content.
>
> For example, if we have an MP4/AAC file at 44.1kHz sampling rate, we would
> expect that specifying 9.75238095238095 (420 frames) would return a
> manifest with the same exact amount of frames throughout.
> Instead, we see the AAC encoder vary the amount of frames without any real
> explanation.
>

Did you try -hls_flags split_by_time ?

Aman

>
> When we run the following command:
>
> /home/ronakp/bin/ffmpeg -i "${FILE}.mp4" -codec copy -hls_time
> 9.75238095238095 -hls_segment_type fmp4 -hls_flags single_file+append_list
> -hls_playlist_type vod "${FILE}_10sec_v7.m3u8"
>
> We get a manifest that looks like so:
>
> #EXTM3U
> #EXT-X-VERSION:7
> #EXT-X-TARGETDURATION:10
> #EXT-X-MEDIA-SEQUENCE:0
> #EXT-X-PLAYLIST-TYPE:VOD
> #EXT-X-MAP:URI="bk_acx0_006556_22_32_10sec_v7.m4s",BYTERANGE="738 at 0"
> #EXT-X-DISCONTINUITY
> #EXTINF:9.798821,
> #EXT-X-BYTERANGE:38733 at 738
> bk_acx0_006556_22_32_10sec_v7.m4s
> #EXTINF:9.752381,
> #EXT-X-BYTERANGE:38531 at 39471
> bk_acx0_006556_22_32_10sec_v7.m4s
> #EXTINF:9.752381,
> #EXT-X-BYTERANGE:38616 at 78002
> bk_acx0_006556_22_32_10sec_v7.m4s
> #EXTINF:9.752381,
> #EXT-X-BYTERANGE:38545 at 116618
> bk_acx0_006556_22_32_10sec_v7.m4s
>
> Notice the first segment there contains 2 more AAC frames...
>
> Now, when we run the following command:
>
> /home/ronakp/bin/ffmpeg -i "${FILE}.mp4" -codec copy -hls_time
> 0.975238095238095 -hls_segment_type fmp4 -hls_flags single_file+append_list
> -hls_playlist_type vod "${FILE}_10sec_v7.m3u8"
>
> #EXTM3U
> #EXT-X-VERSION:7
> #EXT-X-TARGETDURATION:1
> #EXT-X-MEDIA-SEQUENCE:0
> #EXT-X-PLAYLIST-TYPE:VOD
> #EXT-X-MAP:URI="bk_reco_004353_22_32_1sec_v7.m4s",BYTERANGE="738 at 0"
> #EXT-X-DISCONTINUITY
> #EXTINF:0.975238,
> #EXT-X-BYTERANGE:4110 at 738
> bk_reco_004353_22_32_1sec_v7.m4s
> #EXTINF:0.975238,
> #EXT-X-BYTERANGE:3897 at 4848
> bk_reco_004353_22_32_1sec_v7.m4s
> #EXTINF:0.975238,
> #EXT-X-BYTERANGE:4236 at 8745
> bk_reco_004353_22_32_1sec_v7.m4s
> #EXTINF:0.975238,
>
> It seems to have the correct amount of frames everywhere.
>
> Even more bizarre is if we run this command:
>
> /home/ronakp/bin/ffmpeg -i "../${FILE}.mp4" -codec copy -hls_time
> 9.75238095238095 -hls_segment_filename 'file%03d.ts' -hls_segment_type
> mpegts -hls_playlist_type vod "${FILE}_10sec_v3.m3u8"
>
> The manifest looks like the following:
>
> #EXTM3U
> #EXT-X-VERSION:3
> #EXT-X-TARGETDURATION:10
> #EXT-X-MEDIA-SEQUENCE:0
> #EXT-X-PLAYLIST-TYPE:VOD
> #EXTINF:9.799778,
> file000.ts
> #EXTINF:9.706889,
> file001.ts
> #EXTINF:9.753333,
> file002.ts
> #EXTINF:9.799778,
> file003.ts
> #EXTINF:9.753333,
> file004.ts
> #EXTINF:9.706889,
> file005.ts
> #EXTINF:9.799778,
> file006.ts
>
> The ts segments do not all have the same size, and seems like ffmpeg is
> unable to properly honor the supplied time.
>
> And finally, when I run the following command:
>
> /home/ronakp/bin/ffmpeg -i "${FILE}.mp4" -codec copy -f dash
> -single_file_name "${FILE}_1sec.m4s" -min_seg_duration 975238.095238095
> -hls_playlist 1 "${FILE}_1sec.mpd"
>
> I get a manifest that looks like:
>
> #EXTM3U
> #EXT-X-VERSION:6
> #EXT-X-TARGETDURATION:10
> #EXT-X-MEDIA-SEQUENCE:1
> #EXT-X-MAP:URI="bk_reco_004353_22_32_10sec.m4s",BYTERANGE="738 at 0"
> #EXTINF:9.798821,
> #EXT-X-BYTERANGE:38996 at 738
> bk_reco_004353_22_32_10sec.m4s
> #EXTINF:9.798821,
> #EXT-X-BYTERANGE:38754 at 39734
> bk_reco_004353_22_32_10sec.m4s
> #EXTINF:9.798821,
> #EXT-X-BYTERANGE:38765 at 78488
> bk_reco_004353_22_32_10sec.m4s
> #EXTINF:9.798821,
> #EXT-X-BYTERANGE:38583 at 117253
> bk_reco_004353_22_32_10sec.m4s
> #EXTINF:9.798821,
> #EXT-X-BYTERANGE:38752 at 155836
> bk_reco_004353_22_32_10sec.m4s
>
> Where every fragment has 1 extra frame in it.
>
> Can someone please help get this fixed? The fragmentation should have been
> uniform throughout and exactly the same no matter which options I specify
> here.
>
> For reference, I'm using the following versions of ffmpeg:
>
> ffmpeg version N-90757-g2fc12f4 Copyright (c) 2000-2018 the FFmpeg
> developers
>   built with gcc 4.4.6 (GCC) 20110731 (Red Hat 4.4.6-3)
>   configuration: --prefix=/home/ronakp/ffmpeg_build
> --pkg-config-flags=--static --extra-cflags=-I/home/ronakp/ffmpeg_build/include
> --extra-ldflags=-L/home/ronakp/ffmpeg_build/lib --extra-libs=-lpthread
> --extra-libs=-lm --bindir=/home/ronakp/bin --enable-gpl --enable-avisynth
> --enable-libfdk_aac --enable-libmp3lame --enable-libopus --enable-libvorbis
> --enable-nonfree --enable-libvorbis --enable-version3 --disable-ffplay
>   libavutil      56. 15.100 / 56. 15.100
>   libavcodec     58. 19.100 / 58. 19.100
>   libavformat    58. 13.100 / 58. 13.100
>   libavdevice    58.  4.100 / 58.  4.100
>   libavfilter     7. 18.100 /  7. 18.100
>   libswscale      5.  2.100 /  5.  2.100
>   libswresample   3.  2.100 /  3.  2.100
>   libpostproc    55.  2.100 / 55.  2.100
>
> Thanks,
>
> Ronak
>
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