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• FFMPEG Seeking with concat demuxer causes video & audio to be out of sync

  20 février 2023, par Garuuk

  I have a very simple use case that's driving me bananas.

  


  My problem and question :

  


  I'm using ffmpeg version 5.1.2 on a MacOS and i'm using ffmpeg seeking and concat demuxer to cut many 1 minute videos into 15 seconds chopped up over 12 clips where every clip is just 2 seconds from the same video (kind of like a mini teasers for the video). I would really like to not have to re-encode to make the video processing as fast as possible.

  


  First, I take each 1 minute video and cut it up into 12 clips (I do all this programmatically in python fwiw)

  


  ffmpeg -ss 0 -i input.mp4 -t 2 -c copy -y cut_1.mp4
ffmpeg -ss 4 -i input.mp4 -t 2 -c copy -y cut_2.mp4
ffmpeg -ss 8 -i input.mp4 -t 2 -c copy -y cut_3.mp4
...
...


  


  I then write all the output file names to my concat_manifest.txt

  


  file cut_1.mp4
file cut_2.mp4
...
...


  


  Then I run my concat command :

  


  ffmpeg -f concat -i concat_manifest.txt -c copy -y concat_video.mp4


  


  This works really fast but the audio and video at the stitch point get out of sync and sometimes the video just chokes & lags. It's mostly not a smooth experience.

  


  What I have tried :

  


  

  1. using the concat protocol with intermediate profiles : ffmpeg.org/wiki/Concatenate#demuxer

  


  2. Putting the -ss when I seek after the -i. This makes everything worse

  


  3. Playing around with different -ss values. This has some noticeable affects but it's not obvious why yet.

  


  4. I've also read from the ffmpeg resource regarding seeking and copying :

  


  


  Which leads me to believe that maybe because ffmpeg is using timestamps instead of frames, seeking isn't accurate using -ss when using the concat demuxer

  


  Is there a way to get concat demuxer cutting and concatenating the video where the audio is somewhat in sync with the video ?

  


  Thanks

  


  EDIT : I found an answer and i'll be posting the solution in the coming few days.

  


• ERROR : Cannot Autodetect input stream or No signal

  23 juin 2022, par Damián Devera

  I am using Decklink Mini Recorder to capture video (it has SDI and HDMI inputs, tried both).

  


  This is my setup : Debian 10.2.1 (non GUI), ffmpeg 5.0, Blackmagic software 12.3

  


  For that I installed custom build of ffmpeg :

  


  sudo apt-get update -qq && sudo apt-get -y install \
  autoconf \
  automake \
  build-essential \
  cmake \
  git-core \
  libass-dev \
  libmp3lame-dev \
  libfreetype6-dev \
  libtool \
  libvorbis-dev \
  pkg-config \
  texinfo \
  wget \
  zlib1g-dev
sudo apt-get -y install \
  nasm yasm

sudo apt-get install -y libopus-dev
sudo apt-get install -y libvpx-dev
sudo apt-get install -y libx264-dev
sudo apt-get install -y libx265-dev
sudo apt-get install -y libnuma-dev
sudo apt-get install -y libfdk-aac-dev
sudo apt-get install -y libmp3lame-dev

cd ~/ffmpeg_sources && \
git -C fdk-aac pull 2> /dev/null || git clone --depth 1 https://github.com/mstorsjo/fdk-aac && \
cd fdk-aac && \
autoreconf -fiv && \
./configure --prefix="$HOME/ffmpeg_build" --disable-shared && \
make && \
make install



cd ~/ffmpeg_sources
wget https://ffmpeg.org/releases/ffmpeg-4.1.3.tar.bz2
tar -xvf ffmpeg-*.tar.bz2
cd ffmpeg-*/
PATH="$HOME/bin:$PATH" PKG_CONFIG_PATH="$HOME/ffmpeg_build/lib/pkgconfig" ./configure \
  --prefix="$HOME/ffmpeg_build" \
  --pkg-config-flags="--static" \
  --extra-cflags="-I$HOME/ffmpeg_build/include -I$HOME/ffmpeg_sources/BMD_SDK/include" \
  --extra-ldflags="-L$HOME/ffmpeg_build/lib" \
  --extra-libs="-lpthread -lm" \
  --bindir="$HOME/bin" \
  --enable-gpl \
  --enable-libass \
  --enable-libfdk-aac \
  --enable-libfreetype \
  --enable-libmp3lame \
  --enable-libopus \
  --enable-libvorbis \
  --enable-libvpx \
  --enable-libx264 \
  --enable-libx265 \
  --enable-nonfree \
  --enable-decklink

PATH="$HOME/bin:$PATH" make -j `nproc`
sudo cp ffmpeg ffprobe /usr/local/bin/


  


  I can see my card using Blackmagic softwares for the card and also using ffmpeg -sources decklink.

  


  But when I try to run this : ffmpeg -f decklink -i 'DeckLink Mini Recorder' -t 10 -c:v libx264 -f mp4 test.mp4

  


  I get error : Cannot Autodetect input stream or No signal  DeckLink Mini Recorder: Input/output error

  


  UPDATE 1 : I used new command ffmpeg -y -format_code 23ps -f decklink -i 'DeckLink Mini Recorder' test.mov -report
Now I can run command, but I capture only colour bars.

  


  UPDATE 2 : I used new command ffmpeg -f decklink -video_input hdmi -i ‘DeckLink Mini Recorder’ -t 10 test.mp4
I am now capturing over HDMI.

  


  Now I am trying to use SDI on the card (which is my main target) but running into same problems (using this command : ffmpeg -f decklink -video_input sdi -i ‘DeckLink Mini Recorder’ -t 10 test.mp4). I have HDMI to SDI convertor from BlackMagic (HDMI to SDI 3G). Does anybody know, what is the problem ?

  


• OPensuse does not reboot after installing I install gnutls

  5 septembre 2021, par Harry Boy

  I am trying to build ffmpeg on OpenSuse with the following flags :

  


  ffmpeg-3.4.8 # ./configure --prefix=/usr --libdir=/usr/lib64 --shlibdir=/usr/lib64 --incdir=/usr/include/ffmpeg --extra-cflags='-fmessage-length=0 -grecord-gcc-switches -O2 -Wall -D_FORTIFY_SOURCE=2 -fstack-protector-strong -funwind-tables -fasynchronous-unwind-tables -fstack-clash-protection -g' --optflags='-fmessage-length=0 -grecord-gcc-switches -O2 -Wall -D_FORTIFY_SOURCE=2 -fstack-protector-strong -funwind-tables -fasynchronous-unwind-tables -fstack-clash-protection -g' --disable-htmlpages --enable-pic --disable-stripping --enable-shared --disable-static --enable-gpl --disable-openssl --enable-avresample --enable-libcdio --enable-gnutls --enable-ladspa --enable-libass --enable-libbluray --enable-libcelt --enable-libcdio --enable-libdc1394 --enable-libfreetype --enable-libgsm --enable-libmp3lame --enable-libopenjpeg --enable-libopus --enable-libpulse --enable-libspeex --enable-libtheora --enable-libtwolame --enable-libvidstab --enable-libvorbis --enable-libvpx --enable-libwebp --enable-libzimg --enable-libzvbi --enable-vaapi --enable-vdpau --enable-libopencore-amrnb --enable-libopencore-amrwb --enable-version3 --enable-libx264 --enable-libx265 --enable-libxvid


  


  I get the forrowing error :

  


  ERROR: gnutls not found using pkg-config

If you think configure made a mistake, make sure you are using the latest
version from Git.  If the latest version fails, report the problem to the
ffmpeg-user@ffmpeg.org mailing list or IRC #ffmpeg on irc.freenode.net.
Include the log file "ffbuild/config.log" produced by configure as this will help
solve the problem.


  


  I then install gnutls from this link :
https://software.opensuse.org/package/gnutls

  


  zypper addrepo https://download.opensuse.org/repositories/openSUSE:Leap:15.2:Update/standard/openSUSE:Leap:15.2:Update.repo

zypper refresh
zypper install gnutls
Loading repository data...
Reading installed packages...
Resolving package dependencies...

Problem: nothing provides 'this-is-only-for-build-envs' needed by the to be installed libunbound-devel-mini-1.6.8-lp152.9.3.1.x86_64
Solution 1: do not install gnutls-3.6.7-lp152.9.12.1.x86_64
Solution 2: break libunbound-devel-mini-1.6.8-lp152.9.3.1.x86_64 by ignoring some of its dependencies

Choose from above solutions by number or cancel [1/2/c/d/?] (c): 2
Resolving dependencies...
Resolving package dependencies...

The following 4 NEW packages are going to be installed:
 gnutls libgnutls-dane0 libopts25 libunbound-devel-mini

The following package requires a system reboot:
gnutls

4 new packages to install.
Overall download size: 1.1 MiB. Already cached: 0 B. After the operation, additional 4.0 MiB will be used.

Note: System reboot required.
Continue? [y/n/v/...? shows all options] (y): y
Retrieving package libopts25-5.18.12-lp152.4.3.1.x86_64                                                                                     
(1/4),  65.6 KiB (134.5 KiB unpacked)
Retrieving: libopts25-5.18.12-lp152.4.3.1.x86_64.rpm ......................................................................................................................[done]
Retrieving package libunbound-devel-mini-1.6.8-lp152.9.3.1.x86_64                                                                           (2/4), 331.5 KiB (723.4 KiB unpacked)
Retrieving: libunbound-devel-mini-1.6.8-lp152.9.3.1.x86_64.rpm ............................................................................................................[done]
Retrieving package libgnutls-dane0-3.6.7-lp152.9.12.1.x86_64                                                                                (3/4),  91.7 KiB ( 34.6 KiB unpacked)
Retrieving: libgnutls-dane0-3.6.7-lp152.9.12.1.x86_64.rpm .................................................................................................................[done]
Retrieving package gnutls-3.6.7-lp152.9.12.1.x86_64                                                                                         (4/4), 675.4 KiB (  3.1 MiB unpacked)
Retrieving: gnutls-3.6.7-lp152.9.12.1.x86_64.rpm ..............................................................................................................[done (3.6 MiB/s)]

Checking for file conflicts: ..............................................................................................................................................[done]
(1/4) Installing: libopts25-5.18.12-lp152.4.3.1.x86_64 ....................................................................................................................[done]
(2/4) Installing: libunbound-devel-mini-1.6.8-lp152.9.3.1.x86_64 ..........................................................................................................[done]
(3/4) Installing: libgnutls-dane0-3.6.7-lp152.9.12.1.x86_64 ...............................................................................................................[done]
(4/4) Installing: gnutls-3.6.7-lp152.9.12.1.x86_64 ........................................................................................................................[done]


  


  Note the system reboot hint.
When I reboot my system I it just boots to a black screen. It does not display the logon prompt.
Any ideas as to why this is or how I can debug it ?