Recherche avancée

Sur d’autres sites (11017)

• fftools/ffmpeg_dec : abort if avcodec_send_packet() returns EAGAIN

  22 mai 2023, par James Almer

  fftools/ffmpeg_dec : abort if avcodec_send_packet() returns EAGAIN
  As the comment in the code mentions, EAGAIN is not an expected value here
  
  because we call avcodec_receive_frame() until all frames have been returned.
  
  avcodec_send_packet() returning EAGAIN means a packet is still buffered, which
  
  hints that the underlying decoder is buggy and not fetching packets as it
  
  should.
  An example of this behavior was in the libdav1d wrapper before f209614290,
  
  where feeding it split frames (or individual OBUs) would result in the CLI
  
  eventually printing the confusing "Error submitting packet to decoder : Resource
  
  temporarily unavailable" error message, and just keep going until EOF without
  
  returning new frames.
  Signed-off-by : James Almer <jamrial@gmail.com>
  

  • [DH] fftools/ffmpeg_dec.c

• How to convert from AV_PIX_FMT_BGRA to PIX_FMT_PAL8 ?

  29 juillet 2014, par Jona

  I’m having a hard time converting my images from AV_PIX_FMT_BGRA to PIX_FMT_PAL8. Unfortunately sws_getCachedContext doesn’t support the conversion to PIX_FMT_PAL8.

  What I’m trying to do is convert my images into a GIF video with higher quality output. It seems that PIX_FMT_PAL8 could potentially provide the higher quality output I’m looking for.

  According to this documentation I need to palettize the pixel data, but I have no clue how to do that.

  When the pixel format is palettized RGB (PIX_FMT_PAL8), the palettized
  image data is stored in AVFrame.data[0]. The palette is transported in
  AVFrame.data[1], is 1024 bytes long (256 4-byte entries) and is
  formatted the same as in PIX_FMT_RGB32 described above (i.e., it is
  also endian-specific). Note also that the individual RGB palette
  components stored in AVFrame.data[1] should be in the range 0..255.
  This is important as many custom PAL8 video codecs that were designed
  to run on the IBM VGA graphics adapter use 6-bit palette components.

  Any help or direction would be appreciated.

• RGB to YUV conversion with libav (ffmpeg) triplicates image

  17 avril 2021, par José Tomás Tocino

  I'm building a small program to capture the screen (using X11 MIT-SHM extension) on video. It works well if I create individual PNG files of the captured frames, but now I'm trying to integrate libav (ffmpeg) to create the video and I'm getting... funny results.

  


  The furthest I've been able to reach is this. The expected result (which is a PNG created directly from the RGB data of the XImage file) is this :

  


  

  


  However, the result I'm getting is this :

  


  

  


  As you can see the colors are funky and the image appears cropped three times. I have a loop where I capture the screen, and first I generate the individual PNG files (currently commented in the code below) and then I try to use libswscale to convert from RGB24 to YUV420 :

  


  while (gRunning) {
        printf("Processing frame framecnt=%i \n", framecnt);

        if (!XShmGetImage(display, RootWindow(display, DefaultScreen(display)), img, 0, 0, AllPlanes)) {
            printf("\n Ooops.. Something is wrong.");
            break;
        }

        // PNG generation
        // snprintf(imageName, sizeof(imageName), "salida_%i.png", framecnt);
        // writePngForImage(img, width, height, imageName);

        unsigned long red_mask = img->red_mask;
        unsigned long green_mask = img->green_mask;
        unsigned long blue_mask = img->blue_mask;

        // Write image data
        for (int y = 0; y < height; y++) {
            for (int x = 0; x < width; x++) {
                unsigned long pixel = XGetPixel(img, x, y);

                unsigned char blue = pixel & blue_mask;
                unsigned char green = (pixel & green_mask) >> 8;
                unsigned char red = (pixel & red_mask) >> 16;

                pixel_rgb_data[y * width + x * 3] = red;
                pixel_rgb_data[y * width + x * 3 + 1] = green;
                pixel_rgb_data[y * width + x * 3 + 2] = blue;
            }
        }

        uint8_t* inData[1] = { pixel_rgb_data };
        int inLinesize[1] = { in_w };

        printf("Scaling frame... \n");
        int sliceHeight = sws_scale(sws_context, inData, inLinesize, 0, height, pFrame->data, pFrame->linesize);

        printf("Obtained slice height: %i \n", sliceHeight);
        pFrame->pts = framecnt * (pVideoStream->time_base.den) / ((pVideoStream->time_base.num) * 25);

        printf("Frame pts: %li \n", pFrame->pts);
        int got_picture = 0;

        printf("Encoding frame... \n");
        int ret = avcodec_encode_video2(pCodecCtx, &pkt, pFrame, &got_picture);

//                int ret = avcodec_send_frame(pCodecCtx, pFrame);

        if (ret != 0) {
            printf("Failed to encode! Error: %i\n", ret);
            return -1;
        }

        printf("Succeed to encode frame: %5d - size: %5d\n", framecnt, pkt.size);

        framecnt++;

        pkt.stream_index = pVideoStream->index;
        ret = av_write_frame(pFormatCtx, &pkt);

        if (ret != 0) {
            printf("Error writing frame! Error: %framecnt \n", ret);
            return -1;
        }

        av_packet_unref(&pkt);
    }


  


  I've placed the entire code at this gist. This question right here looks pretty similar to mine, but not quite, and the solution did not work for me, although I think this has something to do with the way the line stride is calculated.