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• vf_idet : Print both the single frame based detection and the multi frame one.

  5 avril 2012, par Michael Niedermayer

  vf_idet : Print both the single frame based detection and the multi frame one.

• Generating a P frame based on an I frame

  17 octobre 2016, par Navid Ahmadi

  Say I have 5 images that are quite similar. I’d like to compress images 2, 3, 4 and 5 based on the first image, somewhat similar to the way P frames are generated from an I frame.

  • In general, what’s the best way/tool to do so ?
  • For instance, using FFMPEG, is it possible to generate P frames and store them in a separate file ?

  Edit :
  Although similar, I am not looking for simply generating a diff between the two images. My goal is to somehow use the information in the first image to make the consecutive images much smaller. If I simply do a diff, the diff itself is about the same size (about 10% reduced) which is not as much as I expect. If I generate a mp4 video including these 5 frames, the video size is much less than putting 5 frames in a file, which probably has to with frame predications based on the I frames. Is there a way to generate those predicted frames one by one and store them individually ?

• How to set h264_qsv encoder based on ffmpeg4.3.1

  17 décembre 2020, par James Sunderland

  I upgrade ffmpeg from 4.1 to 4.3.1 in my project, and i found that video quality get very low(1920x1080 25fps 2048000).
How to config encoder parameters ? Thanks a lot.

  


  AVCodecContext* OpenH264Codec_QSV(int width, int height, int frameRate, int bitRate)
{
    AVCodec* c = avcodec_find_encoder_by_name("h264_qsv");
    AVCodecContext* ctx = avcodec_alloc_context3(c);
    ctx->width = width;
    ctx->height = height;
    ctx->bit_rate = bitRate;
    ctx->time_base.num = 1;
    ctx->time_base.den = frameRate;
    ctx->gop_size = frameRate;
    ctx->bit_rate_tolerance = ctx->bit_rate;
    ctx->rc_max_rate = ctx->bit_rate * 2.0;
    ctx->rc_min_rate = ctx->bit_rate * 0.1;
    //ctx->max_b_frames = 0;
    ctx->max_b_frames = 4;
    ctx->pix_fmt = c->pix_fmts[0];
    av_opt_set(ctx->priv_data, "preset", "medium", 0);
    av_opt_set(ctx->priv_data, "profile", "main", 0);
    av_opt_set(ctx->priv_data, "look_ahead", "0", 0);
    if (avcodec_open2(ctx, c, nullptr) < 0)
    {
        avcodec_free_context(&ctx);
        return nullptr;
    }
    return ctx;
}