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• Multiple files concatenation using ffmpeg by the use of GPU Hardware acceleration

  30 juin 2021, par bubus

  I need to concatenate multiple mp4, h264 encoded files into single one together with speed up filter, using GPU HW acceleration. I am using Debian 10 Buster 64bit, and the card I am using is Nvidia Gainward GTX960.

  


  I have installed CUDA, together with Nvidia driver and configured ffmpeg with the following parameters :

  


  ./configure --enable-nonfree -–enable-cuda-sdk –enable-libnpp --extra-cflags=-I/usr/local/cuda/include --extra-ldflags=-L/usr/local/cuda/lib64`


  


  The problem is, I believe, that GPU is not working at 100%, so the concatenation takes quite a long time.

  


  The command I am using to concatenate files and speeding them up :

  


  ./ffmpeg -c:v h264_cuvid -f concat -i mylist.txt -c:a copy -c:v h264_nvenc -y -filter:v 'setpts='0.0625'*PTS' -an merged.mp4


  


  Output of nvidia-smi while the above command is being executed :

  


  

  


  ffmpeg version: ffmpeg version N-102801-gb74beba9a9
CUDA version: 11.2
Nvidia driver version: 460.84


  


  I have no idea what else can I do to speed up the concatenation.

  


• FFmpeg - how to set output sample_size

  23 décembre 2019, par DennisJ

  Trying to create a simple command line player for .dsf (DSD audio) files, and output to an alsa device that supports up to 24-bit 192 kHz sample rate. The following command almost works and it does play the track. Examining the bold text below, the dsf input file is converted to 24-bit/192 kHz, but the output is then truncated to 16-bit 192 kHz (pcm_s16le i.e, 16 bit little endian).

  ffmpeg -i ’01 - Sweet Georgia Brown.dsf’ -f alsa hw:0,0

  After displaying the ffmpeg banner and song metadata (tags), here is the result, bold is my emphasis :

  Duration : 00:05:14.83, start : 0.000000, bitrate : 9234 kb/s
  Stream #0:0 : Audio : flac, 192000 Hz, stereo, s32 (24 bit)
  Stream mapping :
  Stream #0:0 -> #0:0 (flac (native) -> pcm_s16le (native))
  Press [q] to stop, [?] for help
  Output #0, alsa, to ’hw:0,0’ :

  Since I can play this and many other tracks at full resolution using another player (foobar2000) it seems there might be an option in the encoder which is part of FFmpeg : Lavf57.83.100 I can find no information in any of the FFmpeg documentation that helps. Tried finding options in FFplay and even guessing using other FFmpeg options like this example.
  ffmpeg -sample_fmt s24 -i ’01 - Sweet Georgia Brown.dsf’ -f alsa hw:0,0 ***** same results.

  I’m stuck. Any suggestions ?

  Environment : Linux Mint 19.2, 64-bit, ASUS Xonar STXii sound card.

• Repairing corrupt MOV file

  28 août 2016, par Simon Ridley

  I’m attempting to recover / repair MOV files from a formatted SD card. In the first instance I’ve made a copy of the physical disk using the unix command-line utility "DD". Once that completed I’ve used a working MOV file from the same recording device as a reference file to manually extract the required files using a Hex editor and Python.

  I have attempted to use other recovery tools such as Photorec, and X-Ways, however the extractions appear damaged. This is why I’m using a Hex editor to manually inspect the data to determine what is damaged.

  The software FFMPEG is reporting "moov atom not found" when attempting to process the damaged MOV file.

  When the file is examined in a hex editor I can clearly see that the header appears intact. Offsets 4 to 10 show the ’ftypqt’ signature, then offsets 17 and 16 display ’qt’ and finally the ’mdat’ identifier is at offsets 36 to 39. This is identical to the reference file I have. The mdat container doesn’t appear to finish until ’moov’ which is found at offset 733093392 followed by ’lmvhd’.

  This all appears in the reference file too and as far as I can tell all seems intact. am I correct in thinking that the mdat data is broken in chunks, this is possibly what is referred to as atoms ?

  In which case I appreciate that the data could be damaged somewhere within the mdat. Is it possible to extract the raw data out and rebuild the container ? I’m happy to attempt this with python but I need to understand the structure of the file in more detail. Can anyone help with this please ?