Incorrect segment length in HLS child playlist with fmp4 segment format

[Yash]

Summary of the bug:

I am creating an HLS stream with two resolutions using NVIDIA x264 hardware encoder and FFmpeg is generating a segment with 0 bytes length after init segment in each video child playlist. An example of a child playlist is given below.
How to reproduce:

% ffmpeg -loglevel debug -vsync 0 -hwaccel cuvid -hwaccel_output_format cuda -c:v h264_cuvid -i wanted_1080p.mp4 -y -filter_complex "[0:v]hwdownload,format=nv12[0_v_cpu];[0_v_cpu]colorspace=irange=tv:range=tv:ispace=smpte170m:space=bt709:itrc=smpte170m:trc=bt709:iprimaries=smpte170m:primaries=bt709[init_processed];[init_processed]split=2[360p][720p];[360p]hwupload_cuda,scale_npp=640:360:interp_algo=lanczos[360pScaled];[720p]hwupload_cuda,scale_npp=1280:720:interp_algo=lanczos[720pScaled]" -hls_list_size 0 -hls_playlist_type vod -hls_flags single_file+independent_segments -hls_segment_type fmp4 -hls_segment_filename %v.mp4 -hls_time 2 -master_pl_name 1.m3u8 -preset:v slow -tune:v hq -qmin:v 0 -bf:v 3 -b_ref_mode:v 2 -temporal_aq:v 1 -i_qfactor:v 0.75 -b_qfactor:v 1.1 -color_primaries:v bt709 -color_trc:v bt709 -colorspace:v bt709 -color_range:v tv -g:v 48 -keyint_min:v 48 -forced-idr:v 1 -rc-lookahead:v 0 -no-scenecut:v 1 -map "[360pScaled]" -map "[720pScaled]" -map 0:a:0 -map 0:a:0 -c:v:0 h264_nvenc -c:v:1 h264_nvenc -b:v:0 1499k -b:v:1 2998k -maxrate:v:0 1499k -maxrate:v:1 2998k -bufsize:v:0 2998k -bufsize:v:1 5996k -c:a:0 aac -c:a:1 aac -b:a:0 96k -b:a:1 128k -var_stream_map "v:0,agroup:audio_96k,name:6088fbd10daf052b6b4770cb_0 v:1,agroup:audio_128k,name:6088fbd10daf052b6b4770cb_1 a:0,agroup:audio_96k,name:6088fbd10daf052b6b4770cb_en_96k,language:en a:1,agroup:audio_128k,name:6088fbd10daf052b6b4770cb_en_128k,language:en" -f hls %v.m3u8
ffmpeg version 4.4
built on ...
Ubuntu 20.04 5.8.0-50-generic
CUDA 11.1
Video Codec SDK version 11.0.10.
NVIDIA Driver Version: 460.73.01

6088fbd10daf052b6b4770cb_0.m3u8

#EXTM3U
#EXT-X-VERSION:7
#EXT-X-TARGETDURATION:2
#EXT-X-MEDIA-SEQUENCE:0
#EXT-X-PLAYLIST-TYPE:VOD
#EXT-X-INDEPENDENT-SEGMENTS
#EXT-X-MAP:URI="6088fbd10daf052b6b4770cb_0.mp4",BYTERANGE="450403@0"
#EXTINF:2.000000,
#EXT-X-BYTERANGE:0@450403
6088fbd10daf052b6b4770cb_0.mp4
#EXTINF:2.000000,
#EXT-X-BYTERANGE:359407@450403
6088fbd10daf052b6b4770cb_0.mp4

Truncated child playlist file, please find the whole file in the attachments.

[Yash]

Debug log

[Yash]

360p resolution child playlist

[Yash]

720p resolution child playlist

[Carl Eugen Hoyos]

Please test current FFmpeg git head and provide a log without -hide_banner to make this a valid ticket.

[Yash]

FFmpeg git head debug log

[Yash]

removed '-hide_banner' and added FFmpeg git head command log in attachments.

[Yash]

Also want to mention that the issue seems to be introduced in the 4.4 release, 4.3.2 doesn't have the issue and works perfectly fine (with the same video).

[Jason]

This is likely the same bug and duplicate of this issue: ​https://trac.ffmpeg.org/ticket/9193

[Jason]

I've put up a $150 bounty on this issue.

​https://www.bountysource.com/issues/98201162-incorrect-segment-length-in-hls-child-playlist-with-fmp4-segment-format

[steffend]

If Jason is right, you can try reverting ​https://github.com/FFmpeg/FFmpeg/commit/b5ca8f2c66954614d81579082025f580efc0cffc as described by me in the other issue: ​https://trac.ffmpeg.org/ticket/9193#comment:7

[Yash]

Yes, reverting the mentioned commit resolves the issue.

[Steven Liu]

​https://patchwork.ffmpeg.org/project/ffmpeg/patch/20210501071234.78554-1-liuqi05@kuaishou.com/ Try this patch please

[Carl Eugen Hoyos]

Fixed by Steven in 59032494e81a1a65c0b960aaae7ec4c2cc9db35a

[nyanmisaka]

Hi Steven Liu, could you backport this patch to release/4.4 branch?