[FFmpeg-user] h264 pic_init_qp_minus26 out of range

Mark Thompson sw at jkqxz.net
Sat May 26 22:29:20 EEST 2018

On 24/05/18 12:52, Phillipe Laterrade wrote:
> Setting the qpmin parameter to 12 changes (and reduce) the pic_init_qp_minus26...
> Is it the right way to fix this issue?

Well, what is going wrong with the existing values?  They are allowed by the standard so all decoders supporting >8-bit profiles have to handle then - if you have something which doesn't then you might want to report a bug against it so it can be fixed.

As a workaround for a broken device which doesn't handle the full range of QP, then yes setting qmin to constrain the encoder making the stream is probably a reasonable strategy.

- Mark

> -----Message d'origine-----
> De : ffmpeg-user [mailto:ffmpeg-user-bounces at ffmpeg.org] De la part de Mark Thompson
> Envoyé : jeudi 24 mai 2018 12:22
> À : ffmpeg-user at ffmpeg.org
> Objet : Re: [FFmpeg-user] h264 pic_init_qp_minus26 out of range
> On 24/05/18 10:46, Phillipe Laterrade wrote:
>> Hello,
>> I'm experiencing a problem when transcoding to h264 :
>> The pic_init_qp_minus26 parameter is out of range (-28,-30,-31..) on 
>> some files but not on the whole transcoded files.
> The range of pic_init_qp_minus26 is [-26 - 6 * bit_depth_luma_minus8, +25].  Does your file have a bit depth greater than 8?

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