A question on -tag:v and CPU usage

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A question on -tag:v and CPU usage

Brainiarc7
Hello there,

What impact, if any, does the ffmpeg option -tag:v, when explicitly set,
have on CPU usage?
Does it write the video codec tag per frame, etc?
I ask because I'm seeing some truly abnormal results with hevc_nvenc when
the -tag:v hvc1 option is passed where the CPU load spikes up significantly.

Warm regards,

Dennis.
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Re: A question on -tag:v and CPU usage

kumowoon1025
> Does it write the video codec tag per frame, etc?
Not even, It’s per sample, iirc, but
> I ask because I'm seeing some truly abnormal results with hevc_nvenc when
> the -tag:v hvc1 option is passed where the CPU load spikes up significantly.
hvc1 is the one with codec params in the sample description box, so I guess it’s parsing (basically decoding, as I’ve been told) the stream to copy it to the header. (Or box, I should say, rather. And I’m not sure if it also deletes them after, but I’m pretty sure there’s a separate bsf that does that though.)
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Re: A question on -tag:v and CPU usage

Brainiarc7
On Wed, 30 Oct 2019 at 05:40, Ted Park <[hidden email]> wrote:

> > Does it write the video codec tag per frame, etc?
> Not even, It’s per sample, iirc, but
> > I ask because I'm seeing some truly abnormal results with hevc_nvenc when
> > the -tag:v hvc1 option is passed where the CPU load spikes up
> significantly.
> hvc1 is the one with codec params in the sample description box, so I
> guess it’s parsing (basically decoding, as I’ve been told) the stream to
> copy it to the header. (Or box, I should say, rather. And I’m not sure if
> it also deletes them after, but I’m pretty sure there’s a separate bsf that
> does that though.)
>

Hmm thanks, that second part may explain the spike in CPU load.

>
>
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