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• Access Violation at avcodec_encode_video2()

  23 mars 2016, par bot1131357

  I am trying to understand the FFmpeg API by following online examples available but it seems that the FFmpeg API has changed over time, making most of the examples obsolete ; I hope some of you can help me make more sense of the FFmpeg API examples.

  I am currently trying to understand the encoding-example from FFmpeg, but I am getting an Access Violation error at this line :

  out_size = avcodec_encode_video2(codecCtx, &avpkt, picture, &got_packet);

  where I get "Unhandled exception at 0x77c29e42 in test01_encode.exe : 0xC0000005 : Access violation reading location 0xccccccc8." from Visual Studio.

  I understand that avcodec_encode_video() is deprecated in favour of avcodec_encode_video2(), which uses AVPacket. I’ve allocated a buffer to data member of AVPacket and set its size, but still the same. What did I miss ?

  The library that I’m using is ffmpeg-20160219-git-98a0053-win32-dev. I would really really appreciate if you could help me out of this confusion.

  (Side : What does it mean by "get delayed frames" and why are we encoding by specifying AVFrame* parameter as NULL ?)

  /*
  
   * Video encoding example
  
   */
  
  char filename[] = "test.mpg";
  
  int main(int argc, char** argv)
  
  {
  
      AVCodec *codec;
  
      AVCodecContext *codecCtx= NULL;
  
      int i, out_size, size, x, y, outbuf_size;
  
      FILE *f;
  
      AVFrame *picture;
  
      uint8_t *outbuf, *picture_buf;
  
  
  
      printf("Video encoding\n");
  
  
  
      // Register all formats and codecs
  
      av_register_all();
  
  
  
      /* find the mpeg1 video encoder */
  
      codec = avcodec_find_encoder(AV_CODEC_ID_MPEG1VIDEO);
  
      if (!codec) {
  
          fprintf(stderr, "codec not found\n");
  
          exit(1);
  
      }
  
  
  
      codecCtx= avcodec_alloc_context3(codec);
  
      picture= av_frame_alloc();
  
  
  
      /* put sample parameters */
  
      codecCtx->bit_rate = 400000;
  
      /* resolution must be a multiple of two */
  
      codecCtx->width = 352;
  
      codecCtx->height = 288;
  
      /* frames per second */
  
      //codecCtx->time_base= (AVRational){1,25};
  
      codecCtx->time_base.num = 1;
  
      codecCtx->time_base.den = 25;
  
  
  
      codecCtx->gop_size = 10; /* emit one intra frame every ten frames */
  
      codecCtx->max_b_frames=1;
  
      codecCtx->pix_fmt = AV_PIX_FMT_YUV420P;
  
  
  
      /* open it */
  
      if (avcodec_open2(codecCtx, codec, NULL) < 0) {
  
          fprintf(stderr, "could not open codec\n");
  
          exit(1);
  
      }
  
  
  
      fopen_s(&f,filename, "wb");
  
      if (!f) {
  
          fprintf(stderr, "could not open %s\n", filename);
  
          exit(1);
  
      }
  
  
  
      /* alloc image and output buffer */
  
      outbuf_size = 100000;
  
      outbuf = (uint8_t*) malloc(outbuf_size);
  
      size = codecCtx->width * codecCtx->height;
  
      picture_buf = (uint8_t*) malloc((size * 3) / 2); /* size for YUV 420 */
  
  
  
      picture->data[0] = picture_buf;
  
      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;
  
  
  
      picture->width = codecCtx->width;
  
      picture->height = codecCtx->height;
  
      picture->format = codecCtx->pix_fmt;
  
  
  
      AVPacket avpkt;
  
      int got_packet;
  
  
  
      avpkt.size=av_image_get_buffer_size(codecCtx->pix_fmt, codecCtx->width,
  
                      codecCtx->height,1);    
  
      avpkt.data = (uint8_t *)av_malloc(avpkt.size*sizeof(uint8_t));
  
  
  
      /* encode 1 second of video */
  
      for(i=0;i<25;i++) {
  
          fflush(stdout);
  
          /* prepare a dummy image */
  
          /* 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, outbuf, outbuf_size, picture);
  
          // <access violation="violation"> 
  
          out_size = avcodec_encode_video2(codecCtx, &amp;avpkt, picture, &amp;got_packet); 
  
          printf("encoding frame %3d (size=%5d)\n", i, out_size);
  
          //fwrite(outbuf, 1, out_size, f);
  
          fwrite(avpkt.data, 1, avpkt.size, f);
  
      }
  
  
  
      /* get the delayed frames */
  
      for(; out_size; i++) {
  
          fflush(stdout);
  
  
  
          //out_size = avcodec_encode_video(codecCtx, outbuf, outbuf_size, NULL);
  
          out_size = avcodec_encode_video2(codecCtx, &amp;avpkt, NULL, &amp;got_packet); 
  
          printf("write frame %3d (size=%5d)\n", i, out_size);
  
          //fwrite(outbuf, 1, out_size, f);
  
          fwrite(avpkt.data, 1, avpkt.size, f);
  
      }
  
  
  
      /* add sequence end code to have a real mpeg file */
  
      outbuf[0] = 0x00;
  
      outbuf[1] = 0x00;
  
      outbuf[2] = 0x01;
  
      outbuf[3] = 0xb7;
  
      fwrite(outbuf, 1, 4, f);
  
      fclose(f);
  
      free(picture_buf);
  
      free(outbuf);
  
  
  
      avcodec_close(codecCtx);
  
      av_free(codecCtx);
  
      av_free(picture);
  
      printf("\n");
  
  }
  
  </access>

• H264 decoding using ffmpeg

  14 juillet 2016, par Kindermann

  I’m trying to decode a video stream with ffmpeg library, that’s how I do it basically :

  void video_decode(const char *filename)
  
  {
  
      AVCodec *codec;
  
      AVCodecContext *c= NULL;
  
      int frame_count=0;
  
      FILE *f;
  
      AVFrame *frame;
  
      uint8_t inbuf[INBUF_SIZE + AV_INPUT_BUFFER_PADDING_SIZE];
  
      AVPacket avpkt;
  
      av_init_packet(&avpkt);
  
      memset(inbuf + INBUF_SIZE, 0, AV_INPUT_BUFFER_PADDING_SIZE);
  
      printf("Decoding video file...\n");
  
      /* find the h264 video decoder */
  
      codec = avcodec_find_decoder(AV_CODEC_ID_H264);
  
      c = avcodec_alloc_context3(codec);
  
      c->bit_rate = 400000;
  
      c->width = 1920;
  
      c->height = 1080;
  
  
  
      if (avcodec_open2(c, codec, NULL) < 0) {
  
          fprintf(stderr, "Could not open codec\n");
  
          exit(1);
  
      }
  
      frame = av_frame_alloc();
  
      for (;;) {
  
          avpkt.size = fread(inbuf, 1, INBUF_SIZE, f);         
  
      if (avpkt.size == 0)
  
              break;
  
          avpkt.data = inbuf;
  
          while(avpkt.size > 0){
  
  
  
          int len, got_frame;
  
              len = avcodec_decode_video2(c, frame, &got_frame, &avpkt);          
  
          if (len < 0) {
  
                  fprintf(stderr, "Errr while decding frame %d\n", frame_count);
  
                  exit (1);
  
              }
  
              if (got_frame) {
  
                  //Print out frame information..
  
          }
  
              if (avpkt.data) {
  
                  avpkt.size -= len;
  
                  avpkt.data += len;
  
              }
  
      }               
  
      }  
  
  }

  But I got the following outputs :

  Decoding video file...
  
  [h264 @ 0x303c040] decode_slice_header error
  
  [h264 @ 0x303c040] decode_slice_header error
  
  [h264 @ 0x303c040] decode_slice_header error
  
  [h264 @ 0x303c040] no frame!
  
  Errr while decding frame 0

  Obviously the initiation of codec was incomplete. Do you have experience with h264 api ? Any help would be appreciated.

• Publish RTMP stream to Red5 Server form iOS camera

  7 septembre 2015, par Mohammad Asif

  Please look at following code, I have transformed CMSampleBufferRef into AV_CODEC_ID_H264 but I don’t know how to transmit it to Red5 server.

  Thanks,

  - (void)  captureOutput:(AVCaptureOutput *)captureOutput
  
    didOutputSampleBuffer:(CMSampleBufferRef)sampleBuffer
  
       fromConnection:(AVCaptureConnection *)connection {
  
  
  
  //NSLog(@"This is working ....");
  
  
  
    // [connection setVideoOrientation: [self deviceOrientation] ];
  
  
  
  if( !CMSampleBufferDataIsReady(sampleBuffer) )
  
  {
  
      NSLog( @"sample buffer is not ready. Skipping sample" );
  
      return;
  
  } else {
  
  
  
      if (captureOutput == videoOutput) {
  
  
  
  
  
          CVPixelBufferRef pixelBuffer = CMSampleBufferGetImageBuffer(sampleBuffer);
  
          CVPixelBufferLockBaseAddress(pixelBuffer, 0);
  
  
  
          // access the data
  
          float width = CVPixelBufferGetWidth(pixelBuffer);
  
          float height = CVPixelBufferGetHeight(pixelBuffer);
  
  
  
          //float bytesPerRow = CVPixelBufferGetBytesPerRowOfPlane(pixelBuffer, 0);
  
          unsigned char *rawPixelBase = (unsigned char *)CVPixelBufferGetBaseAddressOfPlane(pixelBuffer, 0);
  
  
  
  
  
          // Convert the raw pixel base to h.264 format
  
  
  
          if (codec == nil) {
  
  
  
              codec = 0;
  
              context = 0;
  
              frame = 0;
  
  
  
              fmt = avformat_alloc_context();
  
              //avformat_write_header(fmt, NULL);
  
  
  
              codec = avcodec_find_encoder(AV_CODEC_ID_H264);
  
  
  
              if (codec == 0) {
  
                  NSLog(@"Codec not found!!");
  
                  return;
  
              }
  
  
  
              context = avcodec_alloc_context3(codec);
  
  
  
              if (!context) {
  
                  NSLog(@"Context no bueno.");
  
                  return;
  
              }
  
  
  
              // Bit rate
  
              context->bit_rate = 400000; // HARD CODE
  
              context->bit_rate_tolerance = 10;
  
              // Resolution
  
  
  
              // Frames Per Second
  
              context->time_base = (AVRational) {1,25};
  
              context->gop_size = 1;
  
              //context->max_b_frames = 1;
  
              context->width = width;
  
              context->height = height;
  
              context->pix_fmt = PIX_FMT_YUV420P;
  
  
  
              // Open the codec
  
              if (avcodec_open2(context, codec, 0) < 0) {
  
                  NSLog(@"Unable to open codec");
  
                  return;
  
              }
  
  
  
              // Create the frame
  
              frame = av_frame_alloc();
  
              if (!frame) {
  
                  NSLog(@"Unable to alloc frame");
  
                  return;
  
              }
  
          }
  
  
  
          context->width = width;
  
          context->height = height;
  
  
  
          frame->format = context->pix_fmt;
  
          frame->width = context->width;
  
          frame->height = context->height;
  
  
  
          //int nbytes = avpicture_get_size(context->pix_fmt, context->width, context->height);
  
          //uint8_t* outbuffer = (uint8_t*)av_malloc(nbytes);
  
  //            AVFrame *pFrameDecoded = avcodec_alloc_frame();
  
  //            int num_bytes2 = avpicture_get_size(context->pix_fmt, frame->width, frame->height);
  
  //            uint8_t* frame2_buffer2 = (uint8_t *)av_malloc(num_bytes2 * sizeof(uint8_t));
  
  //            avpicture_fill((AVPicture*)pFrameDecoded, frame2_buffer2, PIX_FMT_YUVJ422P, 320, 240);
  
  
  
          frame->pts = (1.0 / 30) * 60 * count;
  
          avpicture_fill((AVPicture *) frame, rawPixelBase, context->pix_fmt, frame->width, frame->height);
  
  
  
          int got_output = 0;
  
          av_init_packet(&packet);
  
          //avcodec_encode_video2(context, &packet, frame, &got_output);
  
  
  
          do {
  
              avcodec_encode_video2(context, &packet, frame, &got_output);
  
              //avcodec_decode_video2(context, &packet, NULL, &got_output);
  
              //*... handle received packet*/
  
  
  
              if (isFirstPacket) {
  
                  [rtmp sendCreateStreamPacket];
  
                  isFirstPacket = false;
  
                  //av_dump_format(fmt, 0, [kRtmpEP UTF8String], 1);
  
                  avformat_alloc_output_context2(&ofmt_ctx, NULL, "flv", [kRtmpEP UTF8String]); //RTMP
  
              }
  
  
  
              packet.stream_index = ofmt_ctx->nb_streams;
  
              av_interleaved_write_frame(ofmt_ctx, &packet);
  
              count ++;
  
  
  
              //[rtmp write:[NSData dataWithBytes:packet.data length:packet.size]];
  
  
  
  
  
          } while(got_output);
  
  
  
          // Unlock the pixel data
  
          CVPixelBufferUnlockBaseAddress(pixelBuffer, 0);
  
  
  
          //[rtmp write:[NSData dataWithBytes:packet.data length:packet.size]];
  
  
  
      } else {
  
  
  
      }
  
  }   }