Hi all,
Are these issues being tracked somewhere already? I would like to have this
fixed. I'm happy to send pull requests, but I'll also have to get familiar with
the AAC muxer code.
Where can I start learning that? Is that the best place to look for these
issues?
Ronak
> On May 2, 2018, at 10:59 AM, Ronak Patel <ronak2121-at-yahoo....@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.
>
> 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@0"
> #EXT-X-DISCONTINUITY
> #EXTINF:9.798821,
> #EXT-X-BYTERANGE:38733@738
> bk_acx0_006556_22_32_10sec_v7.m4s
> #EXTINF:9.752381,
> #EXT-X-BYTERANGE:38531@39471
> bk_acx0_006556_22_32_10sec_v7.m4s
> #EXTINF:9.752381,
> #EXT-X-BYTERANGE:38616@78002
> bk_acx0_006556_22_32_10sec_v7.m4s
> #EXTINF:9.752381,
> #EXT-X-BYTERANGE:38545@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@0"
> #EXT-X-DISCONTINUITY
> #EXTINF:0.975238,
> #EXT-X-BYTERANGE:4110@738
> bk_reco_004353_22_32_1sec_v7.m4s
> #EXTINF:0.975238,
> #EXT-X-BYTERANGE:3897@4848
> bk_reco_004353_22_32_1sec_v7.m4s
> #EXTINF:0.975238,
> #EXT-X-BYTERANGE:4236@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@0"
> #EXTINF:9.798821,
> #EXT-X-BYTERANGE:38996@738
> bk_reco_004353_22_32_10sec.m4s
> #EXTINF:9.798821,
> #EXT-X-BYTERANGE:38754@39734
> bk_reco_004353_22_32_10sec.m4s
> #EXTINF:9.798821,
> #EXT-X-BYTERANGE:38765@78488
> bk_reco_004353_22_32_10sec.m4s
> #EXTINF:9.798821,
> #EXT-X-BYTERANGE:38583@117253
> bk_reco_004353_22_32_10sec.m4s
> #EXTINF:9.798821,
> #EXT-X-BYTERANGE:38752@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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