Recherche avancée

Sur d’autres sites (7577)

• How to convert char buffer (with pcm audio data) to short buffer

  18 décembre 2012, par testCoder

  I have char pAudioBuffer buffer which i got from function ffmpeg :

  int len = avcodec_decode_audio3(av_codec_context,
  
              (int16_t *) pAudioBuffer, &out_size, &packet);

  I know that audio format is two bytes per sample, i need to convert every two bytes to short value, i have tried to use code snippet below, but i often got zero instead of short value :

  int shortBufIndex = 0;
  
  for (int i = 0; i < (out_size); i += 2) {
  
      char b1 = pAudioBuffer[i];
  
      char b2 = pAudioBuffer[i + 1];
  
      short sample = atoi(&b1) + atoi(&b2);
  
      shortBuffer[shortBufIndex] = sample;
  
      shortBufIndex++;
  
      LOGI("BUFFER_ITEM='%d'", sample);
  
  }

  What i'm doing wrong, how to convert every two bytes in char buffer to short and and back.

  UPDATE :

  system's byte order is LITTLE_ENDIAN i have test it like this : Endianness of Android NDK

  How can i convert every two bytes in buffer to sample of short type and back. Please can you provide any code sample.

  UPDATE

  I have tried to access to short as pairs, here is my fixed code, but it not work, i don't hear any sound :

      int shortBufIndex = 0;
  
      for (int i = 0; i < (out_size); i += 2) {
  
          char * byte = (char *) pAudioBuffer[i];
  
          short * sample = byte;
  
          shortBuffer[shortBufIndex] = sample;
  
  }

  What i'm doing wrong ?
  I need conversion like this : byte array to short array and back again in java but in c.

• Add frame to video in specified position

  28 septembre 2015, par QUANGPHAT ĐINH

  I’m using Aforge libs to read and write video files (the libs is here : http://www.aforgenet.com/framework/features/ffmpeg.html).

  Now I want to export a specific frame to edit, then import it back to the video.

  I could export frame by frame but I don’t know how to add it back to the video in specific frame. what should i do now ?

• FFmpeg Multi-Line Commands

  31 août 2015, par alr027

  I’m not really a programmer but I started dabbling with FFmpeg to edit mp4 files and have come across a problem. I’m trying to add an mp3 overlay to an mp4 video with it’s own audio track using FFmpeg. I want to keep the original audio as well as the new one. The only way I found is to strip the audio from the original video, combine it with the mp3 file, and then combine that file back with the mp4 :

  ffmpeg -i video.mp4 1.mp3
  
  
  
  ffmpeg -i audio.mp3 -i 1.mp3  -filter_complex amerge -c:a libmp3lame -q:a 4 audiofinal.mp3
  
  
  
  ffmpeg  -i videofinal.mp4 -i audiofinal.mp3 -shortest final.mp4

  That is a fine way of doing it and it works but I have to run my files back and forth through FFmpeg way too many times. How can I write one text file to run all three of these commands in sequence ?

  Also, I’m using Windows.