CODEWITHSUNDEEP
ffmpegh.264video-encodinglossless
Squid
Squid

Reputation: 45

h264 lossless settings in c

I am currently trying to apply lossless H264 settings for FFMPEG in c. However, I am unsure as to what the settings need to be to ensure lossless encoding and I have found little documentation in this area.

My current settings are:

    codecContex->coder_type = 1; 
    codecContex->flags|=CODEC_FLAG_LOOP_FILTER;
    codecContex->flags2|=CODEC_FLAG2_BPYRAMID-CODEC_FLAG2_WPRED-CODEC_FLAG2_8X8DCT;

    codecContex->profile=FF_PROFILE_H264_BASELINE;
    codecContex->scenechange_threshold = 40; 
    codecContex->gop_size=40;
    codecContex->max_b_frames=0;
    codecContex->max_qdiff=4;
    codecContex->me_method=10;
    codecContex->me_range=16;
    codecContex->me_cmp|= 1;
    codecContex->me_subpel_quality = 5; 
    codecContex->qmin=0; 
    codecContex->qmax=0;
    codecContex->qcompress=0.6f;
    codecContex->keyint_min=25;
    codecContex->trellis=0;
    codecContex->level=13;
    codecContex->refs = 16;
    codecContex->weighted_p_pred = 2;
    codecContex->b_frame_strategy= 1;
    codecContex->color_range = libffmpeg::AVCOL_RANGE_JPEG;
    codecContex->coder_type = FF_CODER_TYPE_AC;
    codecContex->crf = 0;

Any ideas as to what they should be to ensure lossless encoding? Thanks in advance.

Upvotes: 2

Views: 2093

Answers (1)

luca
luca

Reputation: 150

Try this:

...
AVDictionary *param;
av_dict_set(&param, "qp", "0", 0);
/*
Change options to trade off compression efficiency against encoding speed. If you specify a preset, the changes it makes will be applied before all other parameters are applied.
You should generally set this option to the slowest you can bear.
Values available: ultrafast, superfast, veryfast, faster, fast, medium, slow, slower, veryslow, placebo.
*/
av_dict_set(&param, "preset", "medium", 0);
/*
Tune options to further optimize them for your input content. If you specify a tuning, the changes will be applied after --preset but before all other parameters.
If your source content matches one of the available tunings you can use this, otherwise leave unset.
Values available: film, animation, grain, stillimage, psnr, ssim, fastdecode, zerolatency.
*/
av_dict_set(&param, "tune", "film", 0);
int rt = avcodec_open2(codecContext, codec, &param);
...

For lossless don't use profile

Upvotes: 2

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