Recherche avancée

Sur d’autres sites (8865)

• How to handle differing .mp4 file types from different sources ?

  10 octobre 2017, par Dave502619

  If I take a .mp4 recorded on my mobile (Samsung S5) and pass it through FFmpeg with the below command, the output file (fileX.avi) is a greyscale bitmap uncompressed video file.

  • The offset values in fileX.avi (output from FFmpeg) to allow me to locate the video frame data are always 5680 bytes for the file header.

  • And 62 bytes for the inter frame header.

  • The data is uncompressed RGB24 so i can easily calculate the size of a video frame from height x width x 3.

  So my C# application can access the video frames in fileX.avi always at these above offsets.
  (This works great).

  My FFmpeg Command is :

  ffmpeg.exe -i source.mp4 -b 1150 -r 20.97 -g 120 -an -vf format=gray -f rawvideo -pixfmt gray -s 384x216 -vcodec rawvideo -y fileX.avi

  However... I recently took an .mp4 file from a different source (produced by Power Director 14 instead of direct from my mobile phone) and used this as the input source.mp4. But now the structure of fileX.avi differs as the offset values of 5680 + 62 bytes from the start in fileX.avi do not land me at the start of the video data frames.

  There seems to be different file formats for .mp4 - and obviously if there are my crude offset approach will not work for them all. I suspected at the time I wrote the code my method was all too easy a solution !

  So can anyone advise on the approach I should take now ? Should I check the original .mp4 or the output file (fileX.avi) to determine a "file type" to which I can determine the different offsets ?

  At the very least I need to be able to identify the "type" of .mp4 file that works so I can declare the type that will work with my software.

• ffmpeg QSV hardware encoder with x11grab screen capture

  11 janvier 2020, par Toby Eggitt

  I believe I have built ffmpeg with support for my motherboard’s Intel graphics processor chip, but I have not succeeded in showing this working in any way. My goal is to use it for screen capture (the ffmpeg I built does capture screen successfully using the software encoding, but this is far too slow to be useful—it manages about 12fps at a very modest quality).

  My main problem—I think—is that I don’t know how to use these encoders, the examples I found all fail, which makes me suspect that what I’ve built is broken in some way. However, I also have no idea how I can verify that I built this correctly, but the following are true :

  • The five components that I built to get to this all compiled without
    errors (they were libva, gmmlib, intel-media-driver, libmfx, and
    ffmpeg
  • The output of ffmpeg -encoders includes four encoders with _qsv in
    their names including h264_qsv
  • Most of the commands I have tried result in output of this form :

      [h264_qsv @ 0x55ef1dc72040] Low power mode is unsupported
  
      [h264_qsv @ 0x55ef1dc72040] Current frame rate is unsupported
  
      [h264_qsv @ 0x55ef1dc72040] Current picture structure is unsupported
  
      [h264_qsv @ 0x55ef1dc72040] Current resolution is unsupported
  
      [h264_qsv @ 0x55ef1dc72040] Current pixel format is unsupported
  
      [h264_qsv @ 0x55ef1dc72040] some encoding parameters are not supported by the QSV runtime. Please double check the input parameters.
  
      Error initializing output stream 0:0 -- Error while opening encoder for output stream #0:0 - maybe incorrect parameters such as bit_rate, rate, width or height

  I have the impression this thing might be fussy about many parameters of this sort but have no idea where to find out what it would like. Any suggestions at all, how to verify it, or better yet, how to issue a command that captures screen and encodes with the hardware, would be most welcome.

• FFMPEG HLS streaming and transcoding on the fly to HTML player - video duration changes while transcoding

  20 août 2019, par Thomas Tho

  I am trying to make a video streaming server and watch videos directly from web browser. The idea is to make the server to stream video from remote server, transcode with different audio format in local server, and then instantly stream to the client (this is specific way I need it to function).
  This is the FFMPEG code im currently using :

  ffmpeg -i "url" -c:v copy -c:a aac -ac 2 -f hls -hls_time 60 -hls_playlist_type event -hls_flags independent_segments out.m3u8

  The HLS stream is attached to the HTML player with hls.js and it works. However, the video duration is constantly changing while video is being transcoded. I have tried to change video duration with JS like $('video').duration = 120;with no luck.

  How do i make the player to display the video file duration instead of stream current transcoded time ?

  I am also planning to implement video seeking but i am clueless. The current idea is to send seeking time to the server, terminate ffmpeg, and start from specific time. However, i think the player might get stuck on loading and will not start playing without reloading.