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• FFMPEG python check if dictionary key exists

  4 février 2021, par Georgi Stoyanov

  I want to check if there is a dictionary key : "data["streams"][1]["codec_name"]" and if there is one to print the values of couple of keys and if not to print "No Audio". Actually if there is no audio the whole data["streams"][1] is missing. Right now the script is always returning No Audio even if the audio exists. What I am doing wrong ?

  


  #!/usr/bin/env python
import subprocess
import json

input_file = raw_input("Please enter the input file path: ")

returned_data = subprocess.check_output(['ffprobe', '-v', 'quiet', '-print_format', 'json', '-show_format', '-show_streams', input_file])
data = json.loads(returned_data.decode('utf-8'))
print "==========================Audio============================="
if 'data["streams"][1]["codec_name"]' in data:
        print "Codec: %s" %(data["streams"][1]["codec_name"])
        print "Sample Rate: %.3f KHz" %(int(data["streams"][1]["sample_rate"])/1000)
        print "Bitrate: %d Kbps" %(int(data["streams"][1]["bit_rate"])/1000)
else:
        print "NO AUDIO"


  


• Failed to execute : 0x80070057, when decoding video via ffmpeg with dxva2

  25 mars 2019, par CD83

  I have successfully implemented a video player using ffmpeg. I am now trying to use hardware decoding but I’m facing a couple issues.
  I found a post that I followed as a starting point here : https://ffmpeg.org/pipermail/libav-user/2014-August/007323.html

  I have updated the code that setup the necessary stuff for the decoder. The updated code is available here : https://drive.google.com/file/d/0B5ufHdoDzA4ieVk5UVpxcDNzRHc/view?usp=sharing

  And this is how I’m using it to initialize the decoder :

  // Prepare the decoding context
  
  AVCodec *codec = nullptr;
  
  _codecContext = _avFormatContext->streams[_streamIndex]->codec;
  
  if ((codec = avcodec_find_decoder(_codecContext->codec_id)) == 0)
  
  {
  
      std::cout << "Unsupported video codec!" << std::endl;
  
      return false;
  
  }
  
  
  
  _codecContext->thread_count = 1;  // Multithreading is apparently not compatible with hardware decoding
  
  InputStream *ist = new InputStream();
  
  ist->hwaccel_id = HWACCEL_AUTO;
  
  ist->hwaccel_device = "dxva2";
  
  ist->dec = codec;
  
  ist->dec_ctx = _codecContext;
  
  _codecContext->coded_width = _width;
  
  _codecContext->coded_height = _height;
  
  
  
  _codecContext->opaque = ist;
  
  dxva2_init(_codecContext);
  
  
  
  _codecContext->get_buffer2 = ist->hwaccel_get_buffer;
  
  _codecContext->get_format = GetHwFormat;
  
  _codecContext->thread_safe_callbacks = 1;
  
  
  
  if (avcodec_open2(_codecContext, codec, nullptr) < 0)
  
  {
  
      std::cout << "Video codec open error" << std::endl;
  
      return false;
  
  }

  And here is the definition of GetHwFormat referenced above :

  AVPixelFormat GetHwFormat(AVCodecContext *s, const AVPixelFormat *pix_fmts)
  
  {
  
      InputStream* ist = (InputStream*)s->opaque;
  
      ist->active_hwaccel_id = HWACCEL_DXVA2;
  
      ist->hwaccel_pix_fmt = AV_PIX_FMT_DXVA2_VLD;
  
      return ist->hwaccel_pix_fmt;
  
  }

  When I open an mp4 (encoded in h264) video that is HD resolution or less, everything seems to be working fine. However, as soon as I try higher resolution videos like 3840x2160, I get the following errors repeatedly :

  Failed to execute: 0x80070057
  
  Hardware accelerator failed to decode picture

  I also start getting the following errors after a few seconds :

  co located POCs unavailable

  And the video is not displayed properly : I get a lot of artifacts all over the video and it is lagging. I checked the first error in the ffmpeg source code. It seems that IDirectXVideoDecoder_Execute fails because of an invalid parameter. Since this is happening withing ffmpeg, there must be something that I’m missing but I can’t figure out what. The only relevant post that I found with this error was because of multithreading but I set the thread_count to 1 before opening the codec.

  This issue is happening on my main computer which has the following specs :

  • i7-4790 CPU @ 3.6GHz
  • RAM 16 GB
  • Intel HD Graphics 4600
  • Windows 8.1

  The same issue is not happening on my second computer which has the following specs :

  • i7 4510U @ 2GHz
  • RAM 8 GB
  • NVIDIA GeForce GTX 750Ti
  • Windows 10

  If I use DXVAChecker on my main computer, it says that my graphics card supports DXVA2 for H264_VLD_*, and I can see that the calls to the Microsoft API are being made (DXVA2_DecodeDeviceCreated, DXVA2_DecodeDeviceBeginFrame, DXVA2_DecodeDeviceGetBuffer, DXVA2_DecodeDeviceExecute, DXVA2_DecodeDeviceEndFrame) while my video is playing.

  I also don’t see any increase of GPU usage (on either computer) between the version with hardware decoding and the version without ; however, I do see a decrease in CPU usage (not as much as I was expecting though). This is also very strange.

  Note that I tried both the Windows release available on the FFmpeg website, and a version that I compiled with —enable-dxva2. I have searched a lot already but I was unable to find what I’m doing wrong.

  Hopefully, someone can help me, or maybe point me to a better example ?

• FFMPEG Combining images to video and streaming in one command line

  12 juillet 2017, par Brindha Kanniah

  Currently, using ffmpeg, I am using two commands on my Terminal to :

  1) create a video from a bunch of images :

  ffmpeg -r 60 -f image2 -s 1920x1080 -i rotated-pano_frame%05d_color_corrected_gradblend.jpg -vcodec libx264 -crf 25 -pix_fmt yuv420p test.mp4

  2) stream the video to a udp address :

  ffmpeg -re -i test.mp4 -c copy -f flv udp://127.0.0.1:48550

  How can I combine these two commands, into one single ffmpeg command ?

  A concern I have is that it takes a couple of minutes to generate the video from the images. Therefore, these commands have to happen serially, whereby the second command waits a few minutes for the first command to be completed, before it ensues.