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• Encoding using ffmpeg library fails

  29 septembre 2012, par Erik Swansson

  I've spent some time looking at the ffmpeg library and setting things up, I'm opening a .flv file. Reading and decoding and the frames, now I'm trying to encode it to MP4 but my packets end up empty.

  My code as follows

  int main (){
  
  
  
      avformat_open_input(&pFC, "c://wav//test2.flv", NULL, NULL);
  
  
  
      po = av_find_stream_info(pFC);
  
  
  
      //ADD LOGIC TO FIND VIDEO STREAM
  
      pCodecC = pFC->streams[0]->codec;
  
  
  
      decoder = avcodec_find_decoder(pCodecC->codec_id);
  
      encoder = avcodec_find_encoder(pCodecC->codec_id);
  
      po = avcodec_open(pCodecC, decoder);
  
  
  
      pCodecE =  avcodec_alloc_context3(encoder);
  
      /* put sample parameters */
  
      pCodecE->bit_rate = 400000;
  
      /* resolution must be a multiple of two */
  
      pCodecE->width = 352;
  
      pCodecE->height = 288;
  
      /* frames per second */
  
      pCodecE->time_base.den = 25;
  
      pCodecE->time_base.num = 1;
  
      pCodecE->gop_size = 10; /* emit one intra frame every ten frames */
  
      pCodecE->max_b_frames=1;
  
      pCodecE->pix_fmt = PIX_FMT_YUV420P;
  
  
  
      if(pCodecC->codec_id == CODEC_ID_H264)
  
          av_opt_set(pCodecE->priv_data, "preset", "slow", 0);
  
  
  
      po =  avcodec_open2(pCodecE, encoder, NULL);
  
  
  
      AVFrame *pFrame;
  
      // Allocate an AVFrame structure
  
  
  
  
  
  
  
      // Allocate video frame
  
      pFrame=avcodec_alloc_frame();
  
      int frameFinished = 0;
  
      int frame = 0;
  
      int gotpacket = 0;
  
  
  
      while(av_read_frame(pFC, &packet) >= 0)
  
      {
  
          if(packet.stream_index==0) //the video stream is 0
  
          {
  
              int len = avcodec_decode_video2(pCodecC, pFrame, &frameFinished, &packet);
  
              if(frameFinished)
  
              {
  
                  printf("frame # %i", frame);
  
  
  
                  po =avcodec_encode_video2(pCodecE, &spacket, pFrame, &gotpacket);
  
                  if(gotpacket)
  
                  {
  
                      printf("packet recieved");
  
                  }
  
                  frame++;
  
              }
  
          }
  
          av_free_packet(&packet);
  
      }
  
  
  
  
  
      printf("encoding done");
  
  
  
      return 0;
  
  }

  Basically everything works up to

   po =avcodec_encode_video2(pCodecE, &spacket, pFrame, &gotpacket);

  Where &gotpacket returns 0, as in an empty frame.

  Not sure what I'm doing wrong.

• How to encode using the FFMpeg in Android (using H263)

  3 juillet 2012, par Kenny910

  I am trying to follow the sample code on encoding in the ffmpeg document and successfully build a application to encode and generate a mp4 file but I face the following problems :

  1) I am using the H263 for encoding but I can only set the width and height of the AVCodecContext to 176x144, for other case (like 720x480 or 640x480) it will return fail.

  2) I can't play the output mp4 file by using the default Android player, isn't it support H263 mp4 file ? p.s. I can play it by using other player

  3) Is there any sample code on encoding other video frame to make a new video (which mean decode the video and encode it back in different quality setting, also i would like to modify the frame content) ?

  Here is my code, thanks !

  JNIEXPORT jint JNICALL Java_com_ffmpeg_encoder_FFEncoder_nativeEncoder(JNIEnv* env, jobject thiz, jstring filename){
  
  
  
  LOGI("nativeEncoder()");
  
  
  
  avcodec_register_all();
  
  avcodec_init();
  
  av_register_all();
  
  
  
  AVCodec         *codec;
  
  AVCodecContext  *codecCtx;
  
  int             i;
  
  int             out_size;
  
  int             size;
  
  int             x;
  
  int             y;
  
  int             output_buffer_size;
  
  FILE            *file;
  
  AVFrame         *picture;
  
  uint8_t         *output_buffer;
  
  uint8_t         *picture_buffer;
  
  
  
  /* Manual Variables */
  
  int             l;
  
  int             fps = 30;
  
  int             videoLength = 5;
  
  
  
  /* find the H263 video encoder */
  
  codec = avcodec_find_encoder(CODEC_ID_H263);
  
  if (!codec) {
  
      LOGI("avcodec_find_encoder() run fail.");
  
  }
  
  
  
  codecCtx = avcodec_alloc_context();
  
  picture = avcodec_alloc_frame();
  
  
  
  /* put sample parameters */
  
  codecCtx->bit_rate = 400000;
  
  /* resolution must be a multiple of two */
  
  codecCtx->width = 176;
  
  codecCtx->height = 144;
  
  /* frames per second */
  
  codecCtx->time_base = (AVRational){1,fps};
  
  codecCtx->pix_fmt = PIX_FMT_YUV420P;
  
  codecCtx->codec_id = CODEC_ID_H263;
  
  codecCtx->codec_type = AVMEDIA_TYPE_VIDEO;
  
  
  
  /* open it */
  
  if (avcodec_open(codecCtx, codec) < 0) {
  
      LOGI("avcodec_open() run fail.");
  
  }
  
  
  
  const char* mfileName = (*env)->GetStringUTFChars(env, filename, 0);
  
  
  
  file = fopen(mfileName, "wb");
  
  if (!file) {
  
      LOGI("fopen() run fail.");
  
  }
  
  
  
  (*env)->ReleaseStringUTFChars(env, filename, mfileName);
  
  
  
  /* alloc image and output buffer */
  
  output_buffer_size = 100000;
  
  output_buffer = malloc(output_buffer_size);
  
  
  
  size = codecCtx->width * codecCtx->height;
  
  picture_buffer = malloc((size * 3) / 2); /* size for YUV 420 */
  
  
  
  picture->data[0] = picture_buffer;
  
  picture->data[1] = picture->data[0] + size;
  
  picture->data[2] = picture->data[1] + size / 4;
  
  picture->linesize[0] = codecCtx->width;
  
  picture->linesize[1] = codecCtx->width / 2;
  
  picture->linesize[2] = codecCtx->width / 2;
  
  
  
  for(l=0;l/encode 1 second of video
  
      for(i=0;i/prepare a dummy image YCbCr
  
          //Y
  
          for(y=0;yheight;y++) {
  
              for(x=0;xwidth;x++) {
  
                  picture->data[0][y * picture->linesize[0] + x] = x + y + i * 3;
  
              }
  
          }
  
  
  
          //Cb and Cr
  
          for(y=0;yheight/2;y++) {
  
              for(x=0;xwidth/2;x++) {
  
                  picture->data[1][y * picture->linesize[1] + x] = 128 + y + i * 2;
  
                  picture->data[2][y * picture->linesize[2] + x] = 64 + x + i * 5;
  
              }
  
          }
  
  
  
          //encode the image
  
          out_size = avcodec_encode_video(codecCtx, output_buffer, output_buffer_size, picture);
  
          fwrite(output_buffer, 1, out_size, file);
  
      }
  
  
  
      //get the delayed frames
  
      for(; out_size; i++) {
  
          out_size = avcodec_encode_video(codecCtx, output_buffer, output_buffer_size, NULL);
  
          fwrite(output_buffer, 1, out_size, file);
  
      }
  
  }
  
  
  
  //add sequence end code to have a real mpeg file
  
  output_buffer[0] = 0x00;
  
  output_buffer[1] = 0x00;
  
  output_buffer[2] = 0x01;
  
  output_buffer[3] = 0xb7;
  
  
  
  fwrite(output_buffer, 1, 4, file);
  
  fclose(file);
  
  free(picture_buffer);
  
  free(output_buffer);
  
  avcodec_close(codecCtx);
  
  av_free(codecCtx);
  
  av_free(picture);
  
  
  
  LOGI("finish");
  
  
  
  return 0; }

• how to extract audio from video using ffmpeg c++

  28 juin 2016, par daenerys

  I am trying to write c++ code on how to extract audio from mp4 format file. I have compiled the examples in ffmpeg library and tried to run the demuxing_decoding.c file. The problem is that on running the code, it starts to decode way more than the actual file size and decodes wrong codec format (the decoded files cant be run).

  here is the demuxing_decoding.c that I am trying to run :

  #include 
  
  
  
  #include <libavutil></libavutil>opt.h>
  
  #include <libavcodec></libavcodec>avcodec.h>
  
  #include <libavutil></libavutil>channel_layout.h>
  
  #include <libavutil></libavutil>common.h>
  
  #include <libavutil></libavutil>imgutils.h>
  
  #include <libavutil></libavutil>mathematics.h>
  
  #include <libavutil></libavutil>samplefmt.h>
  
  
  
  #define INBUF_SIZE 4096
  
  #define AUDIO_INBUF_SIZE 20480
  
  #define AUDIO_REFILL_THRESH 4096
  
  
  
  /* check that a given sample format is supported by the encoder */
  
  static int check_sample_fmt(AVCodec *codec, enum AVSampleFormat sample_fmt)
  
  {
  
      const enum AVSampleFormat *p = codec->sample_fmts;
  
  
  
      while (*p != AV_SAMPLE_FMT_NONE) {
  
          if (*p == sample_fmt)
  
              return 1;
  
          p++;
  
      }
  
      return 0;
  
  }
  
  
  
  /* just pick the highest supported samplerate */
  
  static int select_sample_rate(AVCodec *codec)
  
  {
  
      const int *p;
  
      int best_samplerate = 0;
  
  
  
      if (!codec->supported_samplerates)
  
          return 44100;
  
  
  
      p = codec->supported_samplerates;
  
      while (*p) {
  
          best_samplerate = FFMAX(*p, best_samplerate);
  
          p++;
  
      }
  
      return best_samplerate;
  
  }
  
  
  
  /* select layout with the highest channel count */
  
  static int select_channel_layout(AVCodec *codec)
  
  {
  
      const uint64_t *p;
  
      uint64_t best_ch_layout = 0;
  
      int best_nb_channels   = 0;
  
  
  
      if (!codec->channel_layouts)
  
          return AV_CH_LAYOUT_STEREO;
  
  
  
      p = codec->channel_layouts;
  
      while (*p) {
  
          int nb_channels = av_get_channel_layout_nb_channels(*p);
  
  
  
          if (nb_channels > best_nb_channels) {
  
              best_ch_layout    = *p;
  
              best_nb_channels = nb_channels;
  
          }
  
          p++;
  
      }
  
      return best_ch_layout;
  
  }
  
  
  
  /*
  
   * Audio encoding example
  
   */
  
  static void audio_encode_example(const char *filename)
  
  {
  
      AVCodec *codec;
  
      AVCodecContext *c= NULL;
  
      AVFrame *frame;
  
      AVPacket pkt;
  
      int i, j, k, ret, got_output;
  
      int buffer_size;
  
      FILE *f;
  
      uint16_t *samples;
  
      float t, tincr;
  
  
  
      printf("Encode audio file %s\n", filename);
  
  
  
      /* find the MP2 encoder */
  
      codec = avcodec_find_encoder(AV_CODEC_ID_MP2);
  
      if (!codec) {
  
          fprintf(stderr, "Codec not found\n");
  
          exit(1);
  
      }
  
  
  
      c = avcodec_alloc_context3(codec);
  
      if (!c) {
  
          fprintf(stderr, "Could not allocate audio codec context\n");
  
          exit(1);
  
      }
  
  
  
      /* put sample parameters */
  
      c->bit_rate = 64000;
  
  
  
      /* check that the encoder supports s16 pcm input */
  
      c->sample_fmt = AV_SAMPLE_FMT_S16;
  
      if (!check_sample_fmt(codec, c->sample_fmt)) {
  
          fprintf(stderr, "Encoder does not support sample format %s",
  
                  av_get_sample_fmt_name(c->sample_fmt));
  
          exit(1);
  
      }
  
  
  
      /* select other audio parameters supported by the encoder */
  
      c->sample_rate    = select_sample_rate(codec);
  
      c->channel_layout = select_channel_layout(codec);
  
      c->channels       = av_get_channel_layout_nb_channels(c->channel_layout);
  
  
  
      /* open it */
  
      if (avcodec_open2(c, codec, NULL) &lt; 0) {
  
          fprintf(stderr, "Could not open codec\n");
  
          exit(1);
  
      }
  
  
  
      f = fopen(filename, "wb");
  
      if (!f) {
  
          fprintf(stderr, "Could not open %s\n", filename);
  
          exit(1);
  
      }
  
  
  
      /* frame containing input raw audio */
  
      frame = av_frame_alloc();
  
      if (!frame) {
  
          fprintf(stderr, "Could not allocate audio frame\n");
  
          exit(1);
  
      }
  
  
  
      frame->nb_samples     = c->frame_size;
  
      frame->format         = c->sample_fmt;
  
      frame->channel_layout = c->channel_layout;
  
  
  
      /* the codec gives us the frame size, in samples,
  
       * we calculate the size of the samples buffer in bytes */
  
      buffer_size = av_samples_get_buffer_size(NULL, c->channels, c->frame_size,
  
                                               c->sample_fmt, 0);
  
      if (buffer_size &lt; 0) {
  
          fprintf(stderr, "Could not get sample buffer size\n");
  
          exit(1);
  
      }
  
      samples = av_malloc(buffer_size);
  
      if (!samples) {
  
          fprintf(stderr, "Could not allocate %d bytes for samples buffer\n",
  
                  buffer_size);
  
          exit(1);
  
      }
  
      /* setup the data pointers in the AVFrame */
  
      ret = avcodec_fill_audio_frame(frame, c->channels, c->sample_fmt,
  
                                     (const uint8_t*)samples, buffer_size, 0);
  
      if (ret &lt; 0) {
  
          fprintf(stderr, "Could not setup audio frame\n");
  
          exit(1);
  
      }
  
  
  
      /* encode a single tone sound */
  
      t = 0;
  
      tincr = 2 * M_PI * 440.0 / c->sample_rate;
  
      for (i = 0; i &lt; 200; i++) {
  
          av_init_packet(&amp;pkt);
  
          pkt.data = NULL; // packet data will be allocated by the encoder
  
          pkt.size = 0;
  
  
  
          for (j = 0; j &lt; c->frame_size; j++) {
  
              samples[2*j] = (int)(sin(t) * 10000);
  
  
  
              for (k = 1; k &lt; c->channels; k++)
  
                  samples[2*j + k] = samples[2*j];
  
              t += tincr;
  
          }
  
          /* encode the samples */
  
          ret = avcodec_encode_audio2(c, &amp;pkt, frame, &amp;got_output);
  
          if (ret &lt; 0) {
  
              fprintf(stderr, "Error encoding audio frame\n");
  
              exit(1);
  
          }
  
          if (got_output) {
  
              fwrite(pkt.data, 1, pkt.size, f);
  
              av_free_packet(&amp;pkt);
  
          }
  
      }
  
  
  
      /* get the delayed frames */
  
      for (got_output = 1; got_output; i++) {
  
          ret = avcodec_encode_audio2(c, &amp;pkt, NULL, &amp;got_output);
  
          if (ret &lt; 0) {
  
              fprintf(stderr, "Error encoding frame\n");
  
              exit(1);
  
          }
  
  
  
          if (got_output) {
  
              fwrite(pkt.data, 1, pkt.size, f);
  
              av_free_packet(&amp;pkt);
  
          }
  
      }
  
      fclose(f);
  
  
  
      av_freep(&amp;samples);
  
      av_frame_free(&amp;frame);
  
      avcodec_close(c);
  
      av_free(c);
  
  }
  
  
  
  /*
  
   * Audio decoding.
  
   */
  
  static void audio_decode_example(const char *outfilename, const char *filename)
  
  {
  
      AVCodec *codec;
  
      AVCodecContext *c= NULL;
  
      int len;
  
      FILE *f, *outfile;
  
      uint8_t inbuf[AUDIO_INBUF_SIZE + AV_INPUT_BUFFER_PADDING_SIZE];
  
      AVPacket avpkt;
  
      AVFrame *decoded_frame = NULL;
  
  
  
      av_init_packet(&amp;avpkt);
  
  
  
      printf("Decode audio file %s to %s\n", filename, outfilename);
  
  
  
      /* find the mpeg audio decoder */
  
      codec = avcodec_find_decoder(AV_CODEC_ID_MP2);
  
      if (!codec) {
  
          fprintf(stderr, "Codec not found\n");
  
          exit(1);
  
      }
  
  
  
      c = avcodec_alloc_context3(codec);
  
      if (!c) {
  
          fprintf(stderr, "Could not allocate audio codec context\n");
  
          exit(1);
  
      }
  
  
  
      /* open it */
  
      if (avcodec_open2(c, codec, NULL) &lt; 0) {
  
          fprintf(stderr, "Could not open codec\n");
  
          exit(1);
  
      }
  
  
  
      f = fopen(filename, "rb");
  
      if (!f) {
  
          fprintf(stderr, "Could not open %s\n", filename);
  
          exit(1);
  
      }
  
      outfile = fopen(outfilename, "wb");
  
      if (!outfile) {
  
          av_free(c);
  
          exit(1);
  
      }
  
  
  
      /* decode until eof */
  
      avpkt.data = inbuf;
  
      avpkt.size = fread(inbuf, 1, AUDIO_INBUF_SIZE, f);
  
  
  
      while (avpkt.size > 0) {
  
          int i, ch;
  
          int got_frame = 0;
  
  
  
          if (!decoded_frame) {
  
              if (!(decoded_frame = av_frame_alloc())) {
  
                  fprintf(stderr, "Could not allocate audio frame\n");
  
                  exit(1);
  
              }
  
          }
  
  
  
          len = avcodec_decode_audio4(c, decoded_frame, &amp;got_frame, &amp;avpkt);
  
          if (len &lt; 0) {
  
              fprintf(stderr, "Error while decoding\n");
  
              exit(1);
  
          }
  
          if (got_frame) {
  
              /* if a frame has been decoded, output it */
  
              int data_size = av_get_bytes_per_sample(c->sample_fmt);
  
              if (data_size &lt; 0) {
  
                  /* This should not occur, checking just for paranoia */
  
                  fprintf(stderr, "Failed to calculate data size\n");
  
                  exit(1);
  
              }
  
              for (i=0; inb_samples; i++)
  
                  for (ch=0; chchannels; ch++)
  
                      fwrite(decoded_frame->data[ch] + data_size*i, 1, data_size, outfile);
  
          }
  
          avpkt.size -= len;
  
          avpkt.data += len;
  
          avpkt.dts =
  
          avpkt.pts = AV_NOPTS_VALUE;
  
          if (avpkt.size &lt; AUDIO_REFILL_THRESH) {
  
              /* Refill the input buffer, to avoid trying to decode
  
               * incomplete frames. Instead of this, one could also use
  
               * a parser, or use a proper container format through
  
               * libavformat. */
  
              memmove(inbuf, avpkt.data, avpkt.size);
  
              avpkt.data = inbuf;
  
              len = fread(avpkt.data + avpkt.size, 1,
  
                          AUDIO_INBUF_SIZE - avpkt.size, f);
  
              if (len > 0)
  
                  avpkt.size += len;
  
          }
  
      }
  
  
  
      fclose(outfile);
  
      fclose(f);
  
  
  
      avcodec_close(c);
  
      av_free(c);
  
      av_frame_free(&amp;decoded_frame);
  
  }
  
  
  
  /*
  
   * Video encoding example
  
   */
  
  static void video_encode_example(const char *filename, int codec_id)
  
  {
  
      AVCodec *codec;
  
      AVCodecContext *c= NULL;
  
      int i, ret, x, y, got_output;
  
      FILE *f;
  
      AVFrame *frame;
  
      AVPacket pkt;
  
      uint8_t endcode[] = { 0, 0, 1, 0xb7 };
  
  
  
      printf("Encode video file %s\n", filename);
  
  
  
      /* find the mpeg1 video encoder */
  
      codec = avcodec_find_encoder(codec_id);
  
      if (!codec) {
  
          fprintf(stderr, "Codec not found\n");
  
          exit(1);
  
      }
  
  
  
      c = avcodec_alloc_context3(codec);
  
      if (!c) {
  
          fprintf(stderr, "Could not allocate video codec context\n");
  
          exit(1);
  
      }
  
  
  
      /* put sample parameters */
  
      c->bit_rate = 400000;
  
      /* resolution must be a multiple of two */
  
      c->width = 352;
  
      c->height = 288;
  
      /* frames per second */
  
      c->time_base = (AVRational){1,25};
  
      /* emit one intra frame every ten frames
  
       * check frame pict_type before passing frame
  
       * to encoder, if frame->pict_type is AV_PICTURE_TYPE_I
  
       * then gop_size is ignored and the output of encoder
  
       * will always be I frame irrespective to gop_size
  
       */
  
      c->gop_size = 10;
  
      c->max_b_frames = 1;
  
      c->pix_fmt = AV_PIX_FMT_YUV420P;
  
  
  
      if (codec_id == AV_CODEC_ID_H264)
  
          av_opt_set(c->priv_data, "preset", "slow", 0);
  
  
  
      /* open it */
  
      if (avcodec_open2(c, codec, NULL) &lt; 0) {
  
          fprintf(stderr, "Could not open codec\n");
  
          exit(1);
  
      }
  
  
  
      f = fopen(filename, "wb");
  
      if (!f) {
  
          fprintf(stderr, "Could not open %s\n", filename);
  
          exit(1);
  
      }
  
  
  
      frame = av_frame_alloc();
  
      if (!frame) {
  
          fprintf(stderr, "Could not allocate video frame\n");
  
          exit(1);
  
      }
  
      frame->format = c->pix_fmt;
  
      frame->width  = c->width;
  
      frame->height = c->height;
  
  
  
      /* the image can be allocated by any means and av_image_alloc() is
  
       * just the most convenient way if av_malloc() is to be used */
  
      ret = av_image_alloc(frame->data, frame->linesize, c->width, c->height,
  
                           c->pix_fmt, 32);
  
      if (ret &lt; 0) {
  
          fprintf(stderr, "Could not allocate raw picture buffer\n");
  
          exit(1);
  
      }
  
  
  
      /* encode 1 second of video */
  
      for (i = 0; i &lt; 25; i++) {
  
          av_init_packet(&amp;pkt);
  
          pkt.data = NULL;    // packet data will be allocated by the encoder
  
          pkt.size = 0;
  
  
  
          fflush(stdout);
  
          /* prepare a dummy image */
  
          /* Y */
  
          for (y = 0; y &lt; c->height; y++) {
  
              for (x = 0; x &lt; c->width; x++) {
  
                  frame->data[0][y * frame->linesize[0] + x] = x + y + i * 3;
  
              }
  
          }
  
  
  
          /* Cb and Cr */
  
          for (y = 0; y &lt; c->height/2; y++) {
  
              for (x = 0; x &lt; c->width/2; x++) {
  
                  frame->data[1][y * frame->linesize[1] + x] = 128 + y + i * 2;
  
                  frame->data[2][y * frame->linesize[2] + x] = 64 + x + i * 5;
  
              }
  
          }
  
  
  
          frame->pts = i;
  
  
  
          /* encode the image */
  
          ret = avcodec_encode_video2(c, &amp;pkt, frame, &amp;got_output);
  
          if (ret &lt; 0) {
  
              fprintf(stderr, "Error encoding frame\n");
  
              exit(1);
  
          }
  
  
  
          if (got_output) {
  
              printf("Write frame %3d (size=%5d)\n", i, pkt.size);
  
              fwrite(pkt.data, 1, pkt.size, f);
  
              av_free_packet(&amp;pkt);
  
          }
  
      }
  
  
  
      /* get the delayed frames */
  
      for (got_output = 1; got_output; i++) {
  
          fflush(stdout);
  
  
  
          ret = avcodec_encode_video2(c, &amp;pkt, NULL, &amp;got_output);
  
          if (ret &lt; 0) {
  
              fprintf(stderr, "Error encoding frame\n");
  
              exit(1);
  
          }
  
  
  
          if (got_output) {
  
              printf("Write frame %3d (size=%5d)\n", i, pkt.size);
  
              fwrite(pkt.data, 1, pkt.size, f);
  
              av_free_packet(&amp;pkt);
  
          }
  
      }
  
  
  
      /* add sequence end code to have a real mpeg file */
  
      fwrite(endcode, 1, sizeof(endcode), f);
  
      fclose(f);
  
  
  
      avcodec_close(c);
  
      av_free(c);
  
      av_freep(&amp;frame->data[0]);
  
      av_frame_free(&amp;frame);
  
      printf("\n");
  
  }
  
  
  
  /*
  
   * Video decoding example
  
   */
  
  
  
  static void pgm_save(unsigned char *buf, int wrap, int xsize, int ysize,
  
                       char *filename)
  
  {
  
      FILE *f;
  
      int i;
  
  
  
      f = fopen(filename,"w");
  
      fprintf(f, "P5\n%d %d\n%d\n", xsize, ysize, 255);
  
      for (i = 0; i &lt; ysize; i++)
  
          fwrite(buf + i * wrap, 1, xsize, f);
  
      fclose(f);
  
  }
  
  
  
  static int decode_write_frame(const char *outfilename, AVCodecContext *avctx,
  
                                AVFrame *frame, int *frame_count, AVPacket *pkt, int last)
  
  {
  
      int len, got_frame;
  
      char buf[1024];
  
  
  
      len = avcodec_decode_video2(avctx, frame, &amp;got_frame, pkt);
  
      if (len &lt; 0) {
  
          fprintf(stderr, "Error while decoding frame %d\n", *frame_count);
  
          return len;
  
      }
  
      if (got_frame) {
  
          printf("Saving %sframe %3d\n", last ? "last " : "", *frame_count);
  
          fflush(stdout);
  
  
  
          /* the picture is allocated by the decoder, no need to free it */
  
          snprintf(buf, sizeof(buf), outfilename, *frame_count);
  
          pgm_save(frame->data[0], frame->linesize[0],
  
                   frame->width, frame->height, buf);
  
          (*frame_count)++;
  
      }
  
      if (pkt->data) {
  
          pkt->size -= len;
  
          pkt->data += len;
  
      }
  
      return 0;
  
  }
  
  
  
  static void video_decode_example(const char *outfilename, const char *filename)
  
  {
  
      AVCodec *codec;
  
      AVCodecContext *c= NULL;
  
      int frame_count;
  
      FILE *f;
  
      AVFrame *frame;
  
      uint8_t inbuf[INBUF_SIZE + AV_INPUT_BUFFER_PADDING_SIZE];
  
      AVPacket avpkt;
  
  
  
      av_init_packet(&amp;avpkt);
  
  
  
      /* set end of buffer to 0 (this ensures that no overreading happens for damaged mpeg streams) */
  
      memset(inbuf + INBUF_SIZE, 0, AV_INPUT_BUFFER_PADDING_SIZE);
  
  
  
      printf("Decode video file %s to %s\n", filename, outfilename);
  
  
  
      /* find the mpeg1 video decoder */
  
      codec = avcodec_find_decoder(AV_CODEC_ID_MPEG1VIDEO);
  
      if (!codec) {
  
          fprintf(stderr, "Codec not found\n");
  
          exit(1);
  
      }
  
  
  
      c = avcodec_alloc_context3(codec);
  
      if (!c) {
  
          fprintf(stderr, "Could not allocate video codec context\n");
  
          exit(1);
  
      }
  
  
  
      if (codec->capabilities &amp; AV_CODEC_CAP_TRUNCATED)
  
          c->flags |= AV_CODEC_FLAG_TRUNCATED; // we do not send complete frames
  
  
  
      /* For some codecs, such as msmpeg4 and mpeg4, width and height
  
         MUST be initialized there because this information is not
  
         available in the bitstream. */
  
  
  
      /* open it */
  
      if (avcodec_open2(c, codec, NULL) &lt; 0) {
  
          fprintf(stderr, "Could not open codec\n");
  
          exit(1);
  
      }
  
  
  
      f = fopen(filename, "rb");
  
      if (!f) {
  
          fprintf(stderr, "Could not open %s\n", filename);
  
          exit(1);
  
      }
  
  
  
      frame = av_frame_alloc();
  
      if (!frame) {
  
          fprintf(stderr, "Could not allocate video frame\n");
  
          exit(1);
  
      }
  
  
  
      frame_count = 0;
  
      for (;;) {
  
          avpkt.size = fread(inbuf, 1, INBUF_SIZE, f);
  
          if (avpkt.size == 0)
  
              break;
  
  
  
          /* NOTE1: some codecs are stream based (mpegvideo, mpegaudio)
  
             and this is the only method to use them because you cannot
  
             know the compressed data size before analysing it.
  
  
  
             BUT some other codecs (msmpeg4, mpeg4) are inherently frame
  
             based, so you must call them with all the data for one
  
             frame exactly. You must also initialize 'width' and
  
             'height' before initializing them. */
  
  
  
          /* NOTE2: some codecs allow the raw parameters (frame size,
  
             sample rate) to be changed at any frame. We handle this, so
  
             you should also take care of it */
  
  
  
          /* here, we use a stream based decoder (mpeg1video), so we
  
             feed decoder and see if it could decode a frame */
  
          avpkt.data = inbuf;
  
          while (avpkt.size > 0)
  
              if (decode_write_frame(outfilename, c, frame, &amp;frame_count, &amp;avpkt, 0) &lt; 0)
  
                  exit(1);
  
      }
  
  
  
      /* some codecs, such as MPEG, transmit the I and P frame with a
  
         latency of one frame. You must do the following to have a
  
         chance to get the last frame of the video */
  
      avpkt.data = NULL;
  
      avpkt.size = 0;
  
      decode_write_frame(outfilename, c, frame, &amp;frame_count, &amp;avpkt, 1);
  
  
  
      fclose(f);
  
  
  
      avcodec_close(c);
  
      av_free(c);
  
      av_frame_free(&amp;frame);
  
      printf("\n");
  
  }
  
  
  
  int main(int argc, char **argv)
  
  {
  
      const char *output_type;
  
  
  
      /* register all the codecs */
  
      avcodec_register_all();
  
  
  
      if (argc &lt; 2) {
  
          printf("usage: %s output_type\n"
  
                 "API example program to decode/encode a media stream with libavcodec.\n"
  
                 "This program generates a synthetic stream and encodes it to a file\n"
  
                 "named test.h264, test.mp2 or test.mpg depending on output_type.\n"
  
                 "The encoded stream is then decoded and written to a raw data output.\n"
  
                 "output_type must be chosen between 'h264', 'mp2', 'mpg'.\n",
  
                 argv[0]);
  
          return 1;
  
      }
  
      output_type = argv[1];
  
  
  
      if (!strcmp(output_type, "h264")) {
  
          video_encode_example("test.h264", AV_CODEC_ID_H264);
  
      } else if (!strcmp(output_type, "mp2")) {
  
          audio_encode_example("test.mp2");
  
          audio_decode_example("test.pcm", "test.mp2");
  
      } else if (!strcmp(output_type, "mpg")) {
  
          video_encode_example("test.mpg", AV_CODEC_ID_MPEG1VIDEO);
  
          video_decode_example("test%02d.pgm", "test.mpg");
  
      } else {
  
          fprintf(stderr, "Invalid output type '%s', choose between 'h264', 'mp2', or 'mpg'\n",
  
                  output_type);
  
          return 1;
  
      }
  
  
  
      return 0;
  
  }

  What could be wrong ?
  The command I used is :

  ./demuxing_decoding /home/cortana/Burn.mp4 /home/cortana/Desktop/Burn.mp4 /home/cortana/Desktop/Burn.aac