resize file and output larger

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resize file and output larger

Michele Salerno
Hi, i have this command:

ffmpeg -threads 16 -hwaccel nvdec -hwaccel_output_format cuda -i
input.mp4 -vf scale_cuda=720:480 -c:v h264_nvenc -preset slow
output.mp4

and output
https://pastebin.com/vDL3rLF5?fbclid=IwAR2zk5MbBveBrdp5nhPuSyLhUvdds0VjBgPG3hgpzZhCCcj4C0YZKMs9rRc

because the output file is larger than the original?

Thanks.

Michele
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Re: resize file and output larger

Moritz Barsnick
On Tue, Oct 22, 2019 at 14:18:17 +0200, Michele Salerno wrote:
> Hi, i have this command:
>
> ffmpeg -threads 16 -hwaccel nvdec -hwaccel_output_format cuda -i
> input.mp4 -vf scale_cuda=720:480 -c:v h264_nvenc -preset slow
> output.mp4
>
> and output
> https://pastebin.com/vDL3rLF5?fbclid=IwAR2zk5MbBveBrdp5nhPuSyLhUvdds0VjBgPG3hgpzZhCCcj4C0YZKMs9rRc

That's so little text, you might as well have posted it here (pastebin
content tends to disappear). Fixing that for you:

#Originale
Duration: 00:15:27.49, start: 0.000000, bitrate: 965 kb/s
Stream #0:0(und): Video: h264 (High) (avc1 / 0x31637661), yuv420p, 1280x720, 830 kb/s, 25 fps, 25 tbr, 12800 tbn, 50 tbc (default)
Stream #0:1(und): Audio: aac (LC) (mp4a / 0x6134706D), 44100 Hz, stereo, fltp, 128 kb/s (default)

#Convertito
Duration: 00:15:27.48, start: 0.000000, bitrate: 2131 kb/s
Stream #0:0(und): Video: h264 (Main) (avc1 / 0x31637661), yuv420p, 720x480 [SAR 1:1 DAR 3:2],  1999 kb/s, 25 fps, 25 tbr, 12800 tbn, 50 tbc (default)
Stream #0:1(und): Audio: aac (LC) (mp4a / 0x6134706D), 44100 Hz, stereo, fltp, 127 kb/s (default)

> because the output file is larger than the original?

I don't use nvenc, but this comment seems in line with your result:
https://superuser.com/a/1369307

    "My experience with using nvenc is that you need to tell it what
    bitrate you want -- it defaults to VBR, which is fine, but no
    amount of tuning makes up for the fact that it always wants to give
    you a 2M average bitrate no matter what resolution file you feed
    it."

You may want to try some varying encoder options instead.

Good luck,
Moritz
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Re: resize file and output larger

Michele Salerno
Il giorno mar 22 ott 2019 alle ore 22:02 Moritz Barsnick
<[hidden email]> ha scritto:

>
> On Tue, Oct 22, 2019 at 14:18:17 +0200, Michele Salerno wrote:
> > Hi, i have this command:
> >
> > ffmpeg -threads 16 -hwaccel nvdec -hwaccel_output_format cuda -i
> > input.mp4 -vf scale_cuda=720:480 -c:v h264_nvenc -preset slow
> > output.mp4
> >
> > and output
> > https://pastebin.com/vDL3rLF5?fbclid=IwAR2zk5MbBveBrdp5nhPuSyLhUvdds0VjBgPG3hgpzZhCCcj4C0YZKMs9rRc
>
> That's so little text, you might as well have posted it here (pastebin
> content tends to disappear). Fixing that for you:
>
Thanks.

> #Originale
> Duration: 00:15:27.49, start: 0.000000, bitrate: 965 kb/s
> Stream #0:0(und): Video: h264 (High) (avc1 / 0x31637661), yuv420p, 1280x720, 830 kb/s, 25 fps, 25 tbr, 12800 tbn, 50 tbc (default)
> Stream #0:1(und): Audio: aac (LC) (mp4a / 0x6134706D), 44100 Hz, stereo, fltp, 128 kb/s (default)
>
> #Convertito
> Duration: 00:15:27.48, start: 0.000000, bitrate: 2131 kb/s
> Stream #0:0(und): Video: h264 (Main) (avc1 / 0x31637661), yuv420p, 720x480 [SAR 1:1 DAR 3:2],  1999 kb/s, 25 fps, 25 tbr, 12800 tbn, 50 tbc (default)
> Stream #0:1(und): Audio: aac (LC) (mp4a / 0x6134706D), 44100 Hz, stereo, fltp, 127 kb/s (default)
>
> > because the output file is larger than the original?
>
> I don't use nvenc, but this comment seems in line with your result:
> https://superuser.com/a/1369307
>
>     "My experience with using nvenc is that you need to tell it what
>     bitrate you want -- it defaults to VBR, which is fine, but no
>     amount of tuning makes up for the fact that it always wants to give
>     you a 2M average bitrate no matter what resolution file you feed
>     it."
>
> You may want to try some varying encoder options instead.
>
I have this hw:
CPU: Intel(R) Core(TM) i7-4770 CPU @ 3.40GHz
RAM: Corsair 32Gb
VGA: NVIDIA Corporation GK106 [GeForce GTX 660] (rev a1)
With cuda... what do you suggest?

Thanks.
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