hls mpegts segmentation is not consistent all the way through for audio only MP4s

[Ronak Patel]

Summary of the bug:

Try to generate an HLS stream using an mpegts container using the following command:

~/bin/ffmpeg -i test.mp4 -codec copy -hls_time 0.975238095238095 -hls_segment_type mpegts -hls_flags single_file -hls_playlist_type vod test.m3u8

or

~/bin/ffmpeg -i test.mp4 -codec copy -hls_time 0.975238095238095 -hls_segment_type mpegts -hls_playlist_type vod test.m3u8

Open the m3u8 file, and see that the segmentation is all over the place, sometimes 1 AAC frame less, or a few AAC frames larger than 0.975238095238095 (21 AAC frames at 22050kHz or 42 frames at 44100kHz).

How to reproduce:

-bash-4.1$ ~/bin/ffmpeg -i test.mp4 -codec copy -hls_time 0.975238095238095 -hls_segment_type mpegts -hls_flags single_file+append_list -hls_playlist_type vod test.m3u8
ffmpeg version N-91512-ga5c17cf 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-libfdk_aac --enable-libmp3lame --enable-libopus --enable-nonfree
  libavutil      56. 18.102 / 56. 18.102
  libavcodec     58. 21.106 / 58. 21.106
  libavformat    58. 17.101 / 58. 17.101
  libavdevice    58.  4.101 / 58.  4.101
  libavfilter     7. 26.100 /  7. 26.100
  libswscale      5.  2.100 /  5.  2.100
  libswresample   3.  2.100 /  3.  2.100
  libpostproc    55.  2.100 / 55.  2.100
Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'test.mp4':
  Metadata:
    major_brand     : isom
    minor_version   : 1
    compatible_brands: isom
    creation_time   : 2013-12-08T19:51:00.000000Z
  Duration: 00:11:24.11, start: 0.000000, bitrate: 31 kb/s
    Stream #0:0(und): Audio: aac (LC) (mp4a / 0x6134706D), 22050 Hz, mono, fltp, 30 kb/s (default)
    Metadata:
      creation_time   : 2013-12-08T19:51:00.000000Z
      handler_name    : GPAC ISO Audio Handler
[hls @ 0x22f4200] Opening 'test.ts' for writing
[mpegts @ 0x22e4f00] frame size not set
Output #0, hls, to 'test.m3u8':
  Metadata:
    major_brand     : isom
    minor_version   : 1
    compatible_brands: isom
    encoder         : Lavf58.17.101
    Stream #0:0(und): Audio: aac (LC) (mp4a / 0x6134706D), 22050 Hz, mono, fltp, 30 kb/s (default)
    Metadata:
      creation_time   : 2013-12-08T19:51:00.000000Z
      handler_name    : GPAC ISO Audio Handler
Stream mapping:
  Stream #0:0 -> #0:0 (copy)
Press [q] to stop, [?] for help
size=N/A time=00:11:24.05 bitrate=N/A speed=1.06e+04x    
video:0kB audio:2572kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: unknown

Patches should be submitted to the ffmpeg-devel mailing list and not this bug tracker.

[Ronak Patel]

I've attached an example of an m3u8 file that ffmpeg produces. I have a feeling the warning about "[mpegts @ 0x22e4f00] frame size not set" could be why this is happening?

[Carl Eugen Hoyos]

Did you attach an output instead of an input file?
Is file input necessary or is the issue reproducible with sine input?

[Ronak Patel]

I attached an output file so you can see what I'm talking about. I've seen this behavior happen with any audio file I pass in, it doesn't matter what the input audio file is.

[Carl Eugen Hoyos]

My question was if file input is needed at all or if the issue is also reproducible with filter input.

[Ronak Patel]

Ok that wasn't clear. I don't know what sine is. I've only ever tried this with file input.

[Cigaes]

RTFM: “Make sure to require a closed GOP when encoding and to set the GOP size to fit your segment time constraint.”

[Ronak Patel]

what is a GOP? What is a closed GOP?

[Ronak Patel]

I've attached one of the source audio MP4s where this is happening. Please notice that this is an AUDIO ONLY MP4. There is NO VIDEO involved here. The hls_time parameter should be honored in this playlist, and should do so with the same number of frames in each mpeg-ts segment (not counting the last one).

[Ronak Patel]

Hi, can anyone please show me where this code to segment audio files is located for mpegts?
It seems this code is different from the codepath for fmp4 since that segments perfectly.