[FFmpeg-devel] [PATCH] nvenc: Compensate for hardware trying to mess with aspect ratio of DVD content.

Agatha Hu ahu at nvidia.com
Thu Jan 22 05:15:44 CET 2015

On 2015/1/21 16:00, Reimar Döffinger wrote:
> On 21.01.2015, at 07:17, Agatha Hu <ahu at nvidia.com> wrote:
>> On 2015/1/18 4:01, Philip Langdale wrote:

>> Here's the reply from NVENC engineers
>> It is not same thing as SAR. It is the display aspect ratio i.e width/height = DAR/SAR
>> The calculation below should be like
>> If (avctx->sample_aspect_ratio.num > 0  && avctx->sample_aspect_ratio.den > 0 )
>>     av_reduce(&dw, &dh, avctx->sample_aspect_ratio.num * avctx->width, avctx->sample_aspect_ratio.den * avctx->height, INT_MAX);
> That doesn't answer anything.
> Doing that, to keep the problem description short, creates different results from libx264 and any other encoder we have for DVD resolution which is highly undesirable for consistency and compatibility reasons if nothing else.
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We will fix the issue in driver, overscan compensation will be applied 
to input DAR *only* if the DAR is 4:3 or 16:9, otherwise won't 
unnecessarily modify the aspect ratio for resolutions like 720x480 and 
The fix will be on future driver, I'll let you know when the branch is 

Agatha Hu

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