[FFmpeg-user] Using FFMpeg to produce LL-HLS

[Gyan Doshi]

On 17-02-2020 08:38 pm, Dennis Mungai wrote:
> On Mon, 17 Feb 2020 at 17:26, Simon Brown <simon.k.brown at gmail.com> wrote:
>> On Mon, 17 Feb 2020 at 12:06, Dennis Mungai <dmngaie at gmail.com> wrote:
>>
>>> On Mon, 17 Feb 2020, 14:50 Simon Brown, <simon.k.brown at gmail.com> wrote:
>>>
>>>> I'm trying to reduce the latency of streaming video to a web page.
>>>> I have tried a few options:
>>>> 1) WebRTC - great, but doesn't support interlaced video
>>>> 2) fMP4 - couldn't get a working solution
>>>> 3) HLS - great, plays interlaced video as well, but latency is appalling
>>>> 4) LL-HLS - can't find anything that produces it.
>>>>
>>>> Does FFMpeg support generating LL-HLS?
>>>>
>>>> Regards,
>>>> Simon
>>>>
>>> Yes, though at the moment you'll have to use the dash muxer.
>>>
>>> See ffmpeg -h muxer=dash
>>>
>>> For usage.
>>>
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>>
>> Thanks Dennis,
>> I've read through the options and looked at some examples and have
>> downloaded the latest FFMpeg build from zeranoe (nightly build).  That
>> produces this result:
>>
>> C:\ffmpeg-20200216-8578433-win64-static\bin>ffmpeg.exe -i udp://
>> 127.0.0.1:9034 -codec copy -f dash -seg_duration 1 -frag_duration 0.1
>> -window_size 5 -extra_window_size 5 -single_file 0 -lhls 1 -hls_playlist 1
>> -strict experimental -streaming 1 -adaptation_sets "id=0,streams=v
>> id=1,streams=a" c:\xampp\htdocs\video.m3u8
>> ffmpeg version git-2020-02-16-8578433 Copyright (c) 2000-2020 the FFmpeg
>> developers
>>    built with gcc 9.2.1 (GCC) 20200122
>>    configuration: --enable-gpl --enable-version3 --enable-sdl2
>> --enable-fontconfig --enable-gnutls --enable-iconv --enable-libass
>> --enable-libdav1d --enable-libbluray --enable-libfreetype
>> --enable-libmp3lame --enable-libopencore-amrnb --enable-libopencore-amrwb
>> --enable-libopenjpeg --enable-libopus --enable-libshine --enable-libsnappy
>> --enable-libsoxr --enable-libtheora --enable-libtwolame --enable-libvpx
>> --enable-libwavpack --enable-libwebp --enable-libx264 --enable-libx265
>> --enable-libxml2 --enable-libzimg --enable-lzma --enable-zlib --enable-gmp
>> --enable-libvidstab --enable-libvorbis --enable-libvo-amrwbenc
>> --enable-libmysofa --enable-libspeex --enable-libxvid --enable-libaom
>> --enable-libmfx --enable-ffnvcodec --enable-cuvid --enable-d3d11va
>> --enable-nvenc --enable-nvdec --enable-dxva2 --enable-avisynth
>> --enable-libopenmpt --enable-amf
>>    libavutil      56. 41.100 / 56. 41.100
>>    libavcodec     58. 70.100 / 58. 70.100
>>    libavformat    58. 38.101 / 58. 38.101
>>    libavdevice    58.  9.103 / 58.  9.103
>>    libavfilter     7. 76.100 /  7. 76.100
>>    libswscale      5.  6.100 /  5.  6.100
>>    libswresample   3.  6.100 /  3.  6.100
>>    libpostproc    55.  6.100 / 55.  6.100
>> Input #0, mpegts, from 'udp://127.0.0.1:9034':
>>    Duration: N/A, start: 68873.648600, bitrate: N/A
>>    Program 1
>>      Stream #0:0[0x1100]: Video: h264 (Main) ([27][0][0][0] / 0x001B),
>> yuv420p(tv, progressive), 1920x1080 [SAR 1:1 DAR 16:9], 50 fps, 50 tbr, 90k
>> tbn, 100 tbc
>>      Stream #0:1[0x1110]: Audio: aac (LC) ([15][0][0][0] / 0x000F), 48000
>> Hz, stereo, fltp, 192 kb/s
>> [dash @ 0000022f500c6a40] No bit rate set for stream 0
>> [dash @ 0000022f500c6a40] Opening 'init-stream0.m4s' for writing
>> [mp4 @ 0000022f4e21ac00] Could not find tag for codec h264 in stream #0,
>> codec not currently supported in container
>> Could not write header for output file #0 (incorrect codec parameters ?):
>> Invalid argument
>> Stream mapping:
>>    Stream #0:0 -> #0:0 (copy)
>>    Stream #0:1 -> #0:1 (copy)
>>      Last message repeated 1 times
>>
>> What am I doing wrong?  I thought h264 was supported in HLS/Dash?
>>
>> Regards,
>> Simon
> Hey there,
>
> Try this instead:
>
> ffmpeg.exe -i udp://127.0.0.1:9034 -codec copy -bsf:a aac_adtstoasc
> -flags +global_header -f dash ^
> -seg_duration 1 -frag_duration 0.1 -window_size 5 -extra_window_size 5
> -single_file 0 -lhls 1 -hls_playlist 1 ^
> -strict experimental -streaming 1 -adaptation_sets "id=0,streams=v
> id=1,streams=a" c:\xampp\htdocs\video.m3u8
>
> Then report back.
>
> Btw I'd recommend re-encoding the content wherever possible. A fixed
> GOP size combined with the -flags +cgop with an encoder such as
> libx264 produces the best results.
> The GOP size should ideally be a fraction of the segment length, eg 2
> seconds. The codec neutral option -g 2 should set that for you.

-g is in frames, so -g 50 for a 25 fps stream. Or you could use 
-force_key_frames

Gyan