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• FFmpeg truncates untrunc'ed video

  18 mars 2020, par petrpulc

  Background : Colleague's Panasonic consumer camera had issues with high-capacity SD card and yielded two different types of truncated files (mp4 and mdt) with both header and index corrupted. Both were "fixable" with following steps :

  



  

  1. Locate with hex editor the ascii sequence "mdat" in both a truncated and a corresponding known good file. In mp4 the "mdat" is quite deep in the file as it contains some (but bad) headers, the mdt type almost starts with it.

  


  2. Replace everything up to the "mdat" sequence with known good header. BUT this also means that metadata on length are copied over.

  


  3. Run https://github.com/ponchio/untrunc on the file with corrected header (it refused to run on original files).

  


  4. Profit ! VLC plays the file fine, ffprobe shows correct length. BUT ffmpeg encoding stops at the end timecode of the file I taken the known good header from in step 2.

  


  5. A somewhat ugly solution is to recode the file in VLC (video copy seems to be breaking file up again).

  


  



  I am wondering if I overlooked something ; big time. I guess I do, but simple timecode operations on input file do not seem to have any effect at all.

  



  Is there a way to persuade ffmpeg to encode the whole file that ffprobe and VLC see ?

  



  Files may be provided for analysis on personal basis only, sorry.

  


• FFMPEG Streaming Issue - "Connection Failed : I/O Error"

  25 avril 2023, par 1080Jake

  For a fun project I wanted to see if I could create an SRT stream from an active SDI input (1080i59.94) on a BMD Decklink Quad card. Whenever I try to execute my syntax, I get the following prompt "Connection to srt ://127.0.0.1:1234 failed : I/O error"
Is there anyway to use a debug mode and get more details about what is causing this ? I am very new to FFMPEG and obviously clueless. This is the syntax I am trying to execute -

  


  C:\Users\01>ffmpeg -f decklink -i "DeckLink Quad (8)" -c:v libx265 -preset ultrafast -b:v 5000k -f mpegts srt://127.0.0.1:1234


  


  Full printout here -

  


  C:\Users\01>ffmpeg -f decklink -i "DeckLink Quad (8)" -c:v libx265 -preset ultrafast -b:v 5000k -bufsize 3000k -f mpegts srt://127.0.0.1:1234
ffmpeg version n6.0-ffmpeg-windows-build-helpers Copyright (c) 2000-2023 the FFmpeg developers
  built with gcc 10.2.0 (GCC)
  configuration: --pkg-config=pkg-config --pkg-config-flags=--static --extra-version=ffmpeg-windows-build-helpers --enable-version3 --disable-debug --disable-w32threads --arch=x86_64 --target-os=mingw32 --cross-prefix=/home/runner/work/ffmpeg-stable-autobuild/ffmpeg-stable-autobuild/sandbox/cross_compilers/mingw-w64-x86_64/bin/x86_64-w64-mingw32- --enable-libcaca --enable-gray --enable-libtesseract --enable-fontconfig --enable-gmp --enable-libass --enable-libbluray --enable-libbs2b --enable-libflite --enable-libfreetype --enable-libfribidi --enable-libgme --enable-libgsm --enable-libilbc --enable-libmodplug --enable-libmp3lame --enable-libopencore-amrnb --enable-libopencore-amrwb --enable-libopus --enable-libsnappy --enable-libsoxr --enable-libspeex --enable-libtheora --enable-libtwolame --enable-libvo-amrwbenc --enable-libvorbis --enable-libwebp --enable-libzimg --enable-libzvbi --enable-libmysofa --enable-libopenjpeg --enable-libopenh264 --enable-libvmaf --enable-libsrt --enable-libxml2 --enable-opengl --enable-libdav1d --enable-cuda-llvm --enable-gnutls --enable-libsvtav1 --enable-libvpx --enable-libaom --enable-nvenc --enable-nvdec --extra-libs=-lharfbuzz --extra-libs=-lm --extra-libs=-lshlwapi --extra-libs=-lmpg123 --extra-libs=-lpthread --extra-cflags=-DLIBTWOLAME_STATIC --extra-cflags=-DMODPLUG_STATIC --extra-cflags=-DCACA_STATIC --enable-amf --enable-libmfx --enable-gpl --enable-frei0r --enable-librubberband --enable-libvidstab --enable-libx264 --enable-libx265 --enable-avisynth --enable-libaribb24 --enable-libxvid --enable-libdavs2 --enable-libxavs2 --enable-libxavs --extra-cflags='-mtune=generic' --extra-cflags=-O3 --enable-static --disable-shared --prefix=/home/runner/work/ffmpeg-stable-autobuild/ffmpeg-stable-autobuild/sandbox/cross_compilers/mingw-w64-x86_64/x86_64-w64-mingw32 --enable-nonfree --enable-libfdk-aac --enable-decklink
  libavutil      58.  2.100 / 58.  2.100
  libavcodec     60.  3.100 / 60.  3.100
  libavformat    60.  3.100 / 60.  3.100
  libavdevice    60.  1.100 / 60.  1.100
  libavfilter     9.  3.100 /  9.  3.100
  libswscale      7.  1.100 /  7.  1.100
  libswresample   4. 10.100 /  4. 10.100
  libpostproc    57.  1.100 / 57.  1.100
[decklink @ 000002ad2785a6c0] Autodetected the input mode
[decklink @ 000002ad2785a6c0] Found Decklink mode 1920 x 1080 with rate 29.97(i)
Guessed Channel Layout for Input Stream #0.0 : stereo
Input #0, decklink, from 'DeckLink Quad (8)':
  Duration: N/A, start: 0.000000, bitrate: 995869 kb/s
  Stream #0:0: Audio: pcm_s16le, 48000 Hz, 2 channels, s16, 1536 kb/s
  Stream #0:1: Video: rawvideo (UYVY / 0x59565955), uyvy422(top first), 1920x1080, 994333 kb/s, 29.97 tbr, 1000k tbn
[srt @ 000002ad2a870dc0] Connection to srt://127.0.0.1:1234 failed: I/O error
srt://127.0.0.1:1234: I/O error


  


  Instead of using an SDI input from my BMD card, I also tried to use a local mp4 file on my PC but I get the same prompt. Note - I am running FFMPEG on a Windows 10 PC.

  


• How can I capture audio AND video simultenaous with ffmpeg from an USB capture device

  20 mai 2017, par oban

  I’m capturing a video by means of an USB Terratec Grabster AV350 (which is based on the em2860 chip).

  I don’t succeed to get the audio when it is played . If I play the captured video with vlc or with ffplay I got only 3 seconds sound and then a silence for the rest of the video ...

  During the capturing I don’t get any errors. At the end it indicates the size of the video and audio captured ....

  I’m using the ffmpeg command for this :

  ffmpeg -f alsa -ac 2 -i hw:3 -f video4linux2 -i /dev/video0 -acodec ac3 -ab 128k -vcodec mpeg4 -b 6000k -r 25 test5.avi

  The log is :

  [alsa @ 0x9bcd420]Estimating duration from bitrate, this may be inaccurate
  
  Input #0, alsa, from 'hw:3':
  
  Duration: N/A, start: 69930.998994, bitrate: N/A
  
  Stream #0.0: Audio: pcm_s16le, 44100 Hz, 2 channels, s16, 1411 kb/s
  
  [video4linux2 @ 0x9bf5d30]Estimating duration from bitrate, this may be inaccurate
  
  Input #1, video4linux2, from '/dev/video0':
  
  Duration: N/A, start: 1307111377.654173, bitrate: -2147483 kb/s
  
  Stream #1.0: Video: rawvideo, yuyv422, 720x576, -2147483 kb/s, 1000k tbr, 1000k tbn, 1000k tbc
  
  [ac3 @ 0x9bf9590]No channel layout specified. The encoder will guess the layout, but it might be incorrect.
  
  Output #0, avi, to 'test5.avi':
  
  Metadata:
  
  ISFT : Lavf52.64.2
  
  Stream #0.0: Video: mpeg4, yuv420p, 720x576, q=2-31, 6000 kb/s, 25 tbn, 25 tbc
  
  Stream #0.1: Audio: ac3, 44100 Hz, stereo, s16, 128 kb/s
  
  Stream mapping:
  
  Stream #1.0 -> #0.0
  
  Stream #0.0 -> #0.1
  
  Press [q] to stop encoding
  
  frame= 1283 fps= 25 q=2.3 Lsize= 38677kB time=51.32 bitrate=6173.9kbits/s
  
  **video:37755kB audio:846kB** global headers:0kB muxing overhead 0.198922%

  If I reduce the command for only capturing audio, then the audio file can be played successfully :

  ffmpeg -f alsa -ac 2 -i hw:3,0 -acodec ac3 -ab 128k test5.avi

  [alsa @ 0x8ede420]Estimating duration from bitrate, this may be inaccurate
  
  Input #0, alsa, from 'hw:3,0':
  
  Duration: N/A, start: 70395.998935, bitrate: N/A
  
  Stream #0.0: Audio: pcm_s16le, 44100 Hz, 2 channels, s16, 1411 kb/s
  
  [ac3 @ 0x8eebac0]No channel layout specified. The encoder will guess the layout, but it might be incorrect.
  
  Output #0, avi, to 'test5.avi':
  
  Metadata:
  
  ISFT : Lavf52.64.2
  
  Stream #0.0: Audio: ac3, 44100 Hz, stereo, s16, 128 kb/s
  
  Stream mapping:
  
  Stream #0.0 -> #0.0
  
  Press [q] to stop encoding
  
  size= 227kB time=13.62 bitrate= 136.8kbits/s
  
  **video:0kB audio:213kB** global headers:0kB muxing overhead 6.902375%

  If I run the command for only video capturing then vlc or ffplay can play the video successfully :

  ffmpeg -f video4linux2 -i /dev/video0 -vcodec mpeg4 -b 12000k -r 25 test5.avi

  [video4linux2 @ 0x91d6420]Estimating duration from bitrate, this may be inaccurate
  
  Input #0, video4linux2, from '/dev/video0':
  
  Duration: N/A, start: 1307112044.025687, bitrate: -2147483 kb/s
  
  Stream #0.0: Video: rawvideo, yuyv422, 720x576, -2147483 kb/s, 1000k tbr, 1000k tbn, 1000k tbc
  
  Output #0, avi, to 'test5.avi':
  
  Metadata:
  
  ISFT : Lavf52.64.2
  
  Stream #0.0: Video: mpeg4, yuv420p, 720x576, q=2-31, 12000 kb/s, 25 tbn, 25 tbc
  
  Stream mapping:
  
  Stream #0.0 -> #0.0
  
  Press [q] to stop encoding
  
  frame= 388 fps= 25 q=2.0 Lsize= 12963kB time=15.52 bitrate=6842.5kbits/s
  
  **video:12949kB audio:0kB** global headers:0kB muxing overhead 0.114584%

  Strange behaviour I noticed is that when I tried capturing video and audio, I can not capture the audio afterwards any more,
  unless I unplug the AV350 first.

  The G350 is located at card 3 :

  htpc@htpc-01:/proc/asound/G350/pcm0c$ more info
  
  card: 3
  
  device: 0
  
  subdevice: 0
  
  stream: CAPTURE
  
  id: USB Audio
  
  name: USB Audio
  
  subname: subdevice #0
  
  class: 0
  
  subclass: 0
  
  subdevices_count: 1
  
  subdevices_avail: 1

  The OS is a Linux 2.6.38-8-generic with the Ubuntu Natty Narwhal version

  Any help on how to tackle this issue would be great ....

  Thanks !