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• Decode .wav file and write it into another file using ffmpeg

  16 février 2017, par deshu

  How to decode a .wav file and write it into another file using ffmpeg ?

  I got decoded data by this piece of code :

  -(void)audioDecode:(const char *)outfilename inFileName:(const char *)filename
  
  
  
  {
  
  
  
  const char* input_filename=filename;
  
  
  
      //avcodec_register_all();
  
      av_register_all();
  
      avcodec_register_all();
  
     // av_register_all();
  
      //av_ini
  
  
  
  //    AVFormatContext* container=avformat_alloc_context();
  
  //    if(avformat_open_input(&container,filename,NULL,NULL)<0){
  
  //        NSLog(@"Could not open file");
  
  //    }
  
  
  
      AVCodec *codec;
  
      AVCodecContext *c= NULL;
  
      int len;
  
      FILE *f, *outfile;
  
      uint8_t inbuf[AUDIO_INBUF_SIZE + FF_INPUT_BUFFER_PADDING_SIZE];
  
      AVPacket avpkt;
  
      AVFrame *decoded_frame = NULL;
  
  
  
      av_init_packet(&avpkt);
  
  
  
      printf("Decode audio file %s to %s\n", filename, outfilename);
  
      avcodec_register_all();
  
  
  
      AVFrame* frame = av_frame_alloc();
  
      if (!frame)
  
      {
  
          fprintf(stderr, "Could not allocate audio frame\n");
  
                          exit(1);
  
      }
  
  
  
      AVFormatContext* formatContext = NULL;
  
      /* Opening the file, and check if it has opened */
  
      if (avformat_open_input(&formatContext, filename, NULL, NULL) != 0)
  
      {
  
          av_frame_free(&frame);
  
          NSLog(@"Could not open file");
  
      }
  
  
  
      if (avformat_find_stream_info(formatContext, NULL) < 0)
  
      {
  
          av_frame_free(&frame);
  
          avformat_close_input(&formatContext);
  
  
  
          NSLog(@"Error finding the stream info");
  
      }
  
  
  
          outfile = fopen(outfilename, "wb");
  
          if (!outfile) {
  
              av_free(c);
  
              exit(1);
  
          }
  
  
  
      /* Find the audio Stream, if no audio stream are found, clean and exit */
  
      AVCodec* cdc = NULL;
  
      int streamIndex = av_find_best_stream(formatContext, AVMEDIA_TYPE_AUDIO, -1, -1, &cdc, 0);
  
      if (streamIndex < 0)
  
      {
  
          av_frame_free(&frame);
  
          avformat_close_input(&formatContext);
  
          NSLog(@"Could not find any audio stream in the file");
  
          exit(1);
  
      }
  
  
  
      /* Open the audio stream to read data  in audioStream */
  
      AVStream* audioStream = formatContext->streams[streamIndex];
  
  
  
      /* Initialize the codec context */
  
      AVCodecContext* codecContext = audioStream->codec;
  
      codecContext->codec = cdc;
  
      /* Open the codec, and verify if it has opened */
  
      if (avcodec_open2(codecContext, codecContext->codec, NULL) != 0)
  
      {
  
          av_frame_free(&frame);
  
          avformat_close_input(&formatContext);
  
          NSLog(@"Couldn't open the context with the decoder");
  
          exit(1);
  
      }
  
  
  
      /* Initialize buffer to store compressed packets */
  
      AVPacket readingPacket;
  
      av_init_packet(&readingPacket);
  
      int lenght = 1;
  
      long long int chunk = ((formatContext->bit_rate)*lenght/8);
  
      int j=0;
  
      int count = 0;
  
      //audioChunk output;
  
  
  
  
  
      while(av_read_frame(formatContext, &readingPacket)==0){
  
          //if((count+readingPacket.size)>start){
  
              if(readingPacket.stream_index == audioStream->index){
  
  
  
                  AVPacket decodingPacket = readingPacket;
  
  
  
                  // Audio packets can have multiple audio frames in a single packet
  
                  while (decodingPacket.size > 0){
  
                      // Try to decode the packet into a frame
  
                      // Some frames rely on multiple packets, so we have to make sure the frame is finished before
  
                      // we can use it
  
                      int gotFrame = 0;
  
                      int result = avcodec_decode_audio4(codecContext, frame, &gotFrame, &decodingPacket);
  
  
  
                      count += result;
  
  
  
                      if (result >= 0 && gotFrame)
  
                      {
  
                          decodingPacket.size -= result;
  
                          decodingPacket.data += result;
  
                          int a;
  
  
  
                          for(int i=0;idata[0], 1, decodingPacket.size, outfile);
  
  //                            *(output.data+j)=frame->data[0][i];
  
  //
  
                              j++;
  
                              if(j>=chunk) break;
  
                          }
  
  
  
                          // We now have a fully decoded audio frame
  
                      }
  
                      else
  
                      {
  
                          decodingPacket.size = 0;
  
                          decodingPacket.data = NULL;
  
                      }
  
                     // if(j>=chunk) break;
  
                  }
  
              }
  
  //        }else count+=readingPacket.size;
  
  //        
  
  //        // To prevent memory leak, must free packet.
  
  //        av_free_packet(&readingPacket);
  
  //        if(j>=chunk) break;
  
      }
  
      fclose(outfile);

  But the file is created with zero bytes. I don’t know what’s wrong with this code. And I got one more error : "Format adp detected only with low score of 25, misdetection possible !"

• How to create videos with small file size but large resolution ?

  13 février 2017, par Gregory Magarshak

  Is there a programmatic way to create videos that capture, essentially, a powerpoint presentation, that would be not much larger than the audio + screenshots of the powerpoint itself ?

  I want to make software that produces videos with the full resolution of a powerpoint on a large screen, and with a person speaking over it and wvwn doodling. Kind of like "bcontext" software. And then I want to export videos for youtube and other places to be hosted. But I want them to be SMALL. So they can be downloaded by people with slow connections eg in India.

  What factors can affect video size and how can i take advantage of the relative "stillness" of most pixels at most times to make the compression preserve the full sharpness and yet take advantage of the lack of visual changes ? What software do you recommend ?

• Error : The path is not of a legal form while using NReco.VideoConverter

  26 janvier 2017, par Dyon

  I am trying to convert a .flac-file to a .wav-file using NReco.VideoConverter, but I keep getting an error and I do not know why.
  This is the piece of code I am using for the conversion :

          //Create the NReco.VideoConverter.FFMpegConverter object
  
          var ffmpeg = new FFMpegConverter();
  
  
  
          //inputFile will be something like this:
  
          //type: string, "C:\\some\\folder\\fullTrackName" + ".flac"
  
          var inputFile = Path.Combine(downloadFolder + fullTrackNameNoExtension + ".flac");
  
  
  
          //outputFile will be something like this:
  
          //type: string, "C:\\some\\folder\\musicfile" + ".wav"
  
          var outputFile = Path.Combine(downloadFolder + fullTrackNameNoExtension + ".wav");
  
  
  
          //Convert the file using NReco.VideoConverter.FFMpegConverter
  
          ffmpeg.ConvertMedia(inputFile, outputFile, null);

  inputFile/outputFile would be like this, this is what I see when I insert a breakpoint and check the values of in/outputFile :

  string, inputFile/outputFile : "Z :\Downloads\Audio - File (Original Mix).flac" (or .wav)

  And this is the error I receive when I run ffmpeg.ConvertMedia :

  System.ArgumentException: The path is not of a legal form.
  
     at System.IO.Path.LegacyNormalizePath(String path, Boolean fullCheck, Int32 maxPathLength, Boolean expandShortPaths)
  
     at System.IO.Path.NormalizePath(String path, Boolean fullCheck, Int32 maxPathLength, Boolean expandShortPaths)
  
     at System.IO.Path.GetFullPathInternal(String path)
  
     at System.IO.File.InternalGetLastWriteTimeUtc(String path, Boolean checkHost)
  
     at NReco.VideoConverter.FFMpegConverter.EnsureFFMpegLibs()
  
     at NReco.VideoConverter.FFMpegConverter.ConvertMedia(Media input, Media output, ConvertSettings settings)
  
     at NReco.VideoConverter.FFMpegConverter.ConvertMedia(String inputFile, String inputFormat, String outputFile, String outputFormat, ConvertSettings settings)
  
     at NReco.VideoConverter.FFMpegConverter.ConvertMedia(String inputFile, String outputFile, String outputFormat)
  
     at APPLICATION_Name.APPLICATION_Class.ConvertFile(String downloadFolder, String fullTrackName, String fullTrackNameNoExtension, String downloadQuality, String downloadType) in X:\APPLICATION_Name\DownloadTrack.cs:line 244