I'm trying to use FFmpeg to simulate a "live" DASH-LL from a file. However,
the audio "m4s" files and the video "m4s" files are not being created at the
same rate.
The video files lag significantly behind the audio (i.e., they don't exist).
This causes issues with the player since it tries to fetch both audio and video
segments with a given index. e.g. it tries to fetch chunk-stream0-018.m4s and
chunk-stream1-018.m4s but the stream0 chunk (video) hasn't yet been created by
FFmpeg causing the player to give a 404 error.
For example, encoding just 60 seconds ends up with these files in the web root
folder:
init-stream0.m4s
init-stream1.m4s
chunk-stream0-00001.m4s chunk-stream1-00019.m4s
chunk-stream0-00002.m4s chunk-stream1-00020.m4s
chunk-stream0-00003.m4s chunk-stream1-00021.m4s
chunk-stream0-00004.m4s chunk-stream1-00022.m4s
chunk-stream0-00005.m4s chunk-stream1-00023.m4s
chunk-stream0-00006.m4s chunk-stream1-00024.m4s
chunk-stream0-00007.m4s chunk-stream1-00025.m4s
chunk-stream0-00008.m4s chunk-stream1-00026.m4s
chunk-stream0-00009.m4s chunk-stream1-00027.m4s
chunk-stream0-00010.m4s chunk-stream1-00028.m4s
chunk-stream0-00011.m4s chunk-stream1-00029.m4s
chunk-stream0-00012.m4s chunk-stream1-00030.m4s
chunk-stream1-00031.m4s
So the player requests chunk-stream0-29.m4s which gives a 404 error because it
doesn't exist yet.
The command line is:
ffmpeg -loglevel info -re -i
/mnt/swdevel/TestStreams/H264/ThreeHourLongMovie.mp4 -t 60 \
-c:v libx264 -x264-params keyint=120:scenecut=0 -b:v 1M -c:a copy \
-f dash -dash_segment_type mp4 \
-seg_duration 2 \
-target_latency 3 \
-frag_type duration \
-frag_duration 0.2 \
-window_size 10 \
-extra_window_size 3 \
-streaming 1 \
-ldash 1 \
-use_template 1 \
-use_timeline 0 \
-write_prft 1 \
-fflags +nobuffer+flush_packets \
-format_options "movflags=+cmaf" \
-utc_timing_url "/pelican/testPlayers/time.php" \
master.mpd
The <SegmentTemplate> in the MPD file shows the same timescale and duration for
both stream0 and stream1:
<SegmentTemplate timescale="1000000" duration="2000000"
availabilityTimeOffset="1.800"
initialization="init-stream$RepresentationID$.m4s"
media="chunk-stream$RepresentationID$-$Number%05d$.m4s" startNumber="1">
Both dash.js and shaka player and the stream doesn't play. I've also tried
using a VLSI hardware encoder instead of libx264 but same result so the issue
is the the mixer (??)
Any suggestions on how fix this?
Danny
OS: Centos 8
ffmpeg version 4.3.1 Copyright (c) 2000-2020 the FFmpeg developers
built with gcc 8 (GCC)
configuration: --extra-ldflags='-L/mnt/swdevel/Torque/lib3p64 -L/lib'
--extra-cflags='-I/mnt/swdevel/Torque/include
-I/mnt/swdevel/Torque/ext/extinclude/ -I/include' --disable-static
--enable-shared --disable-cuda --disable-cuvid --disable-nvenc --enable-libx264
--enable-gpl --enable-libfreetype --enable-libfontconfig --enable-libv4l2
--enable-indev=alsa --enable-indev=v4l2 --bindir=/mnt/swdevel/Torque/bin64
--datadir=/mnt/swdevel/Torque/ext/ffmpeg-build
--docdir=/mnt/swdevel/Torque/ext/doc --libdir=/mnt/swdevel/Torque/lib3p64
--shlibdir=/mnt/swdevel/Torque/lib3p64
--incdir=/mnt/swdevel/Torque/ext/extinclude/ffmpeg
--mandir=/mnt/swdevel/Torque/ext/ffmpeg-build64 --enable-libxcoder
--disable-doc --enable-x86asm --extra-ldflags=-lm --enable-pthreads
--extra-libs=-lpthread --disable-debug
libavutil 56. 51.100 / 56. 51.100
libavcodec 58. 91.100 / 58. 91.100
libavformat 58. 45.100 / 58. 45.100
libavdevice 58. 10.100 / 58. 10.100
libavfilter 7. 85.100 / 7. 85.100
libswscale 5. 7.100 / 5. 7.100
libswresample 3. 7.100 / 3. 7.100
libpostproc 55. 7.100 / 55. 7.100
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