>>>> Hello,
>>>>
>>>> I've been experimenting with encoding with a cuda card, and I noticed
>>>> that setting the pict_type member of the AVFrame structure to
>>>> AV_PICTURE_TYPE_I >does not trigger it to encode the next frame as an IDR
>>>> frame as libx264 does. I looked at the nvidia docs and it appears there is
>>>> a mechanism for this behavior.
>>
>>> Is that behaviour documented anywhere?
>>
>> I found documentation on the nvidia site
>> (https://developer.nvidia.com/nvencode), here is the section of the document
>> that I referred to in my previous post...
>
>I'm talking about ffmpeg AVFrames.
>I was not aware libx264 even did that, and I don't see any documentation that
>it's possible to force an IDR/I frame that way.
>
>It should be trivial to add the same behaviour to nvenc.
Not exactly documented completely, but I found out about it when I look at the
libx264 options output by the command "ffmpeg -h encoder=libx264" which lists a
-forced_idr option. After seeing that I looked into libx264.c and found the
area where it switches on frame->pict_type and sets the corresponding
X264Context members.
Here is the code from libx264.c, X264_frame function. Its indispensable when
dealing with live RTP streams and recovering from packet loss.
switch (frame->pict_type) {
case AV_PICTURE_TYPE_I:
x4->pic.i_type = x4->forced_idr >= 0 ? X264_TYPE_IDR
: X264_TYPE_KEYFRAME;
break;
case AV_PICTURE_TYPE_P:
x4->pic.i_type = X264_TYPE_P;
break;
case AV_PICTURE_TYPE_B:
x4->pic.i_type = X264_TYPE_B;
break;
default:
x4->pic.i_type = X264_TYPE_AUTO;
break;
}
I'm trying to put together a patch, but I'm struggling a bit setting up to
build.
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