[FFmpeg-user] Hanging bat file and general encoding questions

Moritz Barsnick barsnick at gmx.net
Fri Sep 18 21:40:24 CEST 2015

On Fri, Sep 18, 2015 at 13:59:52 -0400, dreeder quasareg.com wrote:

> C:\...\ffmpeg\bin\ffmpeg -i rtsp:// -b:v 128k -vcodec
> copy -r 30 -t 3600 -y "C:\...\TestRecord\Recording.avi"
> As I have been lead to understand, this doesn't actually reencode, it just dumps
> the stream into a file so there's minimal strain on the cpu.

That's right. "-c:v copy" (or "-vcodec copy") will pass the
demultiplexed input video stream directly on to the output multiplexer.
The CPU needs to do no encoding, but is still busy with demuxing and
muxing, though both are usually much less strain.

Note that this implies that the "-b:v 128k" in your command line is
nonsense. Bandwidth control is an encoder option, a copied streams's
bandwidth is just what it is and can't be changed. (Neither can your
video be resized or any other image manipulating filter applied.)

> without hardware encoding and then try to record from 10 cameras
> simultaneously and the cpu is going to melt trying to encode it all

It's always up to experiments. Note that you can trade off bandwidth
(size), CPU strain (or encoding speed) and video quality against each
other when encoding. But if you don't need to re-encode, you're fine
off with copying the stream.

> libpostproc 54. 0.100 / 54. 0.100<----------------------------------------- I
> have to use Ctrl-C or else it will hang here indefinitely.

I can't help you here.


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