[FFmpeg-devel] qmax limit 28 in mpegvideo_enc.c

Jaka Bac jakabac at gmail.com
Thu Sep 15 15:00:01 EEST 2022


Hello,

mpegvideo_enc.c contains this check in ff_mpv_encode_init:

    if (s->q_scale_type == 1) {
        if (avctx->qmax > 28) {
            av_log(avctx, AV_LOG_ERROR,
                   "non linear quant only supports qmax <= 28 currently\n");
            return AVERROR_PATCHWELCOME;
        }
    }

This was added in:
avcodec/mpeg12enc: extend QP range to 28 for non linear quantizers
https://github.com/FFmpeg/FFmpeg/commit/bf2474c74f2c0b956c069f50483c7d104d856d8b


After a while there was another commit:
avcodec/mpeg12enc: Basic support for encoding non even QPs for
-non_linear_quant 1
https://github.com/FFmpeg/FFmpeg/commit/58fe57d5a05ad8d15c320b2bd163debbc412bdd3

I may be completely wrong, but to me it looks like that the second commit
lifts the "qmax <= 28 restriction".
Or am I missing something?

Thanks,
Jaka


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