[FFmpeg-user] 4K 60Hz Directshow Video Capture

[Roger Pack]

consider also libx264 "ultrafast" preset, GL!

On Tue, Feb 13, 2018 at 7:57 AM, Alex P <alex.p at avenview.com> wrote:

> I think I've figured it out. When I use nv12 or yuv420p as the input and
> output pixel format, I get x1 performance. If I use bgr24/rgb24 as the
> input and yuv444p as the output, I get around x0.3.
>
> But even when I use bgr0 for the input and output, I get less than x1.
> Does anyone know what exactly bgr0 is? I can't find any information about
> it in my googling.
>
> In your testing James, what was the pixel format?
>
> -----Original Message-----
> From: ffmpeg-user [mailto:ffmpeg-user-bounces at ffmpeg.org] On Behalf Of
> James Girotti
> Sent: Monday, February 12, 2018 7:03 PM
> To: FFmpeg user questions
> Subject: Re: [FFmpeg-user] 4K 60Hz Directshow Video Capture
>
> >
> > ffmpeg -f dshow -video_size 3840x2160 -framerate 60000/1001 -rtbufsize
> > 2100000000 -pixel_format bgr24 -i video="MZ0380 PCI, Analog 01 Capture"
> > -c:v h264_nvenc -preset lossless -f null - Gives me the same error
> >
>
> That's surprising, I can get about 200fps using file-based/ramdisk "-c:v
> h264_nvenc -preset -lossless". Have you also tried "-c:v hevc_nvenc -preset
> lossless"? What's the encoding FPS that you're getting? You technically
> shouldn't be able get much more than 60fps as that's what your capture card
> is supplying. Can you monitor the "Video Engine Utilization" during
> encoding? In linux it's listed in the nvidia-settings GUI or "nvidia-smi
> dmon" on the CLI will show enc/dec%.
>
>
> > ffmpeg -f dshow -video_size 3840x2160 -framerate 60000/1001 -rtbufsize
> > 2100000000 -pixel_format bgr24 -i video="MZ0380 PCI, Analog 01 Capture"
> > -c:v rawvideo -f null -
> > Gets me nearly x1 performance when executing from a ram disk but
> >
> > ffmpeg -f dshow -video_size 3840x2160 -framerate 60000/1001 -rtbufsize
> > 2100000000 -pixel_format bgr24 -i video="MZ0380 PCI, Analog 01 Capture"
> > -c:v rawvideo raw.nut
> > Only gets me x0.5 and the buffer overflows.
>
>
> > Is there a way of accelerating rawvideo decoding? Would using my
> > colleagues 1080 make a difference? Thanks.
>
>
> I think raw-video is already decoded. So no way/need to accelerate that.
> You might try a different pix_fmt from your capture card while using
> hw-encoding, but you'd have to test. I don't know the internals, i.e. when
> the pixel format is converted during hw-encoding. So it might make a
> difference.
>
> Changing pixel formats might be a concern if you are trying to achieve
> "100% lossless" capture. I've read that yuv444p should be sufficient
> colorspace for bgr24.
>
> There isn't a lot of info out there on encoding speed differences based on
> GPU models. It's a complex subject, but from what I have observed the ASIC
> is tied to the GPU clock (I have observed that GPU clock speed increases as
> ASIC load increases). If that's true, then a GTX 1080, with it's higher max
> clock, could have faster encoding, but I have no data to back that up only.
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