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• Extract playable parts from unfinished torrent video ?

  9 avril 2016, par MostafaZ4

  Torrents download files by pieces.
  Is it possible to extract downloaded parts from unfinished torrent of a movie into a video that contains only the downloaded parts ??

• How AVCodecContext bitrate, framerate and timebase is used when encoding single frame

  28 mars 2023, par Cyrus

  I am trying to learn FFmpeg from examples as there is a tight schedule. The task is to encode a raw YUV image into JPEG format of the given width and height. I have found examples from ffmpeg official website, which turns out to be quite straight-forward. However there are some fields in AVCodecContext that I thought only makes sense when encoding videos(e.g. bitrate, framerate, timebase, gopsize, max_b_frames etc).

  


  I understand on a high level what those values are when it comes to videos, but do I need to care about those when I just want a single image ? Currently for testing, I am just setting them as dummy values and it seems to work. But I want to make sure that I am not making terrible assumptions that will break in the long run.

  


  EDIT :

  


  Here is the code I got. Most of them are copy and paste from examples, with some changes to replace old APIs with newer ones.

  


  #include "thumbnail.h"
#include "libavcodec/avcodec.h"
#include "libavutil/imgutils.h"
#include 
#include 
#include 

void print_averror(int error_code) {
    char err_msg[100] = {0};
    av_strerror(error_code, err_msg, 100);
    printf("Reason: %s\n", err_msg);
}

ffmpeg_status_t save_yuv_as_jpeg(uint8_t* source_buffer, char* output_thumbnail_filename, int thumbnail_width, int thumbnail_height) {
    const AVCodec* mjpeg_codec = avcodec_find_encoder(AV_CODEC_ID_MJPEG);
    if (!mjpeg_codec) {
        printf("Codec for mjpeg cannot be found.\n");
        return FFMPEG_THUMBNAIL_CODEC_NOT_FOUND;
    }

    AVCodecContext* codec_ctx = avcodec_alloc_context3(mjpeg_codec);
    if (!codec_ctx) {
        printf("Codec context cannot be allocated for the given mjpeg codec.\n");
        return FFMPEG_THUMBNAIL_ALLOC_CONTEXT_FAILED;
    }

    AVPacket* pkt = av_packet_alloc();
    if (!pkt) {
        printf("Thumbnail packet cannot be allocated.\n");
        return FFMPEG_THUMBNAIL_ALLOC_PACKET_FAILED;
    }

    AVFrame* frame = av_frame_alloc();
    if (!frame) {
        printf("Thumbnail frame cannot be allocated.\n");
        return FFMPEG_THUMBNAIL_ALLOC_FRAME_FAILED;
    }

    // The part that I don't understand
    codec_ctx->bit_rate = 400000;
    codec_ctx->width = thumbnail_width;
    codec_ctx->height = thumbnail_height;
    codec_ctx->time_base = (AVRational){1, 25};
    codec_ctx->framerate = (AVRational){1, 25};

    codec_ctx->gop_size = 10;
    codec_ctx->max_b_frames = 1;
    codec_ctx->pix_fmt = AV_PIX_FMT_YUV420P;
    int ret = av_image_fill_arrays(frame->data, frame->linesize, source_buffer, AV_PIX_FMT_YUV420P, thumbnail_width, thumbnail_height, 32);
    if (ret < 0) {
        print_averror(ret);
        printf("Pixel format: yuv420p, width: %d, height: %d\n", thumbnail_width, thumbnail_height);
        return FFMPEG_THUMBNAIL_FILL_FRAME_DATA_FAILED;
    }

    ret = avcodec_send_frame(codec_ctx, frame);
    if (ret < 0) {
        print_averror(ret);
        printf("Failed to send frame to encoder.\n");
        return FFMPEG_THUMBNAIL_FILL_SEND_FRAME_FAILED;
    }

    ret = avcodec_receive_packet(codec_ctx, pkt);
    if (ret < 0) {
        print_averror(ret);
        printf("Failed to receive packet from encoder.\n");
        return FFMPEG_THUMBNAIL_FILL_SEND_FRAME_FAILED;
    }

    // store the thumbnail in output
    int fd = open(output_thumbnail_filename, O_CREAT | O_RDWR);
    write(fd, pkt->data, pkt->size);
    close(fd);

    // freeing allocated structs
    avcodec_free_context(&codec_ctx);
    av_frame_free(&frame);
    av_packet_free(&pkt);
    return FFMPEG_SUCCESS;
}


  


• No such file or directory : 'ffprobe' : 'ffprobe'

  27 novembre 2023, par Jack McCumber

  I'm hoping someone can point me in the right direction. I'm currently trying to build a python GUI that plays clips of sounds from a specified file and allows the user to annotate it. All the research I've done has pointed my to using pydub. I'm using the following snippet :

  


  from pydub import AudioSegment
from pydub.playback import play

song = AudioSegment.from_wav("beepboop.mp3")
play(song)


  


  However, I'm currently getting the following error :

  


  Warning (from warnings module):&#xA;  File "/Library/Frameworks/Python.framework/Versions/3.7/lib/python3.7/site-packages/pydub/utils.py", line 170&#xA;    warn("Couldn&#x27;t find ffmpeg or avconv - defaulting to ffmpeg, but may not work", RuntimeWarning)&#xA;RuntimeWarning: Couldn&#x27;t find ffmpeg or avconv - defaulting to ffmpeg, but may not work&#xA;&#xA;Warning (from warnings module):&#xA;  File "/Library/Frameworks/Python.framework/Versions/3.7/lib/python3.7/site-packages/pydub/utils.py", line 198&#xA;    warn("Couldn&#x27;t find ffprobe or avprobe - defaulting to ffprobe, but may not work", RuntimeWarning)&#xA;RuntimeWarning: Couldn&#x27;t find ffprobe or avprobe - defaulting to ffprobe, but may not work&#xA;Traceback (most recent call last):&#xA;  File "/Users/jack/Desktop/code-repo/convert-csv-to-json/cleaner.py", line 7, in <module>&#xA;    song = AudioSegment.from_wav("beepboop.mp3")&#xA;  File "/Library/Frameworks/Python.framework/Versions/3.7/lib/python3.7/site-packages/pydub/audio_segment.py", line 808, in from_wav&#xA;    return cls.from_file(file, &#x27;wav&#x27;, parameters=parameters)&#xA;  File "/Library/Frameworks/Python.framework/Versions/3.7/lib/python3.7/site-packages/pydub/audio_segment.py", line 728, in from_file&#xA;    info = mediainfo_json(orig_file, read_ahead_limit=read_ahead_limit)&#xA;  File "/Library/Frameworks/Python.framework/Versions/3.7/lib/python3.7/site-packages/pydub/utils.py", line 274, in mediainfo_json&#xA;    res = Popen(command, stdin=stdin_parameter, stdout=PIPE, stderr=PIPE)&#xA;  File "/Library/Frameworks/Python.framework/Versions/3.7/lib/python3.7/subprocess.py", line 775, in __init__&#xA;    restore_signals, start_new_session)&#xA;  File "/Library/Frameworks/Python.framework/Versions/3.7/lib/python3.7/subprocess.py", line 1522, in _execute_child&#xA;    raise child_exception_type(errno_num, err_msg, err_filename)&#xA;FileNotFoundError: [Errno 2] No such file or directory: &#x27;ffprobe&#x27;: &#x27;ffprobe&#x27;&#xA;</module>

  


  I've downloaded both ffprobe and ffmpeg from the official website, extracted the files, and installed to usr/local/bin based on input I've read in other StackOverflow comments. When I run :

  


  print(os.environ['PATH'])


  


  I get :

  


  /usr/bin:/bin:/usr/sbin:/sbin


  


  Also, MacOSX won't let me manually drag the executable into /usr/bin or /usr/sbin. Nor will it let me copy it into the directory using :

  


  $ sudo cp ffmpeg /usr/bin


  


  When I use :

  


  pip3 install ffprobe-python


  


  I get :

  


  Requirement already satisfied: ffprobe-python in /Library/Frameworks/Python.framework/Versions/3.7/lib/python3.7/site-packages (1.0.3)


  


  I'll add that when I try and use the "apt install" method, it barks at me and says my version of MacOSX isn't supported.