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• Creating thumbnail using ffmpeg for video downloaded from youtube

  24 septembre 2015, par akhila

  Thanks in advance. I have trouble creating thumbnail for videos downloaded from youtube . I have downloaded videos using the youtube downloader extension and saved to mp4 format , When I upload a video to my site I use ffmpeg to create the thumbnail of the videos , For other mp4 videos it works perfectly fine but for youtube videos. Youtube videos are uploaded to the site and thumbnail creation not working. Here goes my code.

       system('ffmpeg -i '.$saveimgpath1.' -ss 00:00:00.010 -vframes 1 '.$thumbpath);

  The path given is correct as it works for other videos.Any help will be greatly appreciated .

• FFmpeg can't stream AAC files from stdin ?

  23 janvier 2020, par ffxsam

  I’m having trouble getting FFmpeg to convert an AAC file to HLS chunks :

  cat file.m4a | ffmpeg -y -i pipe:0 -c:a libmp3lame -q:a 0 -map 0:0 -f segment -segment_time 10 -segment_list ./segments.m3u8 -segment_format mpegts -vn ./segment_%03d.ts

  This is being executed in Node.js in a Lambda function (streaming from AWS S3 - the command line above is just for testing purposes).

  The relevant error I get is :

  Stream mapping:
  
    Stream #0:0 -> #0:0 (aac (native) -> mp3 (libmp3lame))
  
  [mov,mp4,m4a,3gp,3g2,mj2 @ 0x397e640] stream 0, offset 0x28: partial file
  
  pipe:0: Invalid data found when processing input

  If I do -i file.m4a, it works perfectly fine. It’s not a deal-breaker, but it would be nice to be able to use stdin, which works OK for MP3 and WAV files.

• 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.