[FFmpeg-user] Help with -video_size

[Roger Pack]

On 1/6/17, Tim Hiles <thiles at confex.com> wrote:
> Hi Moritz, Roger
>
> Hi Moritz
>
>>
>> >
>> > Can you be a bit more clear? Are you trying to record the full 1366x768
>> > and resize it to 1024x768, or are you trying to capture only 1024x768
>> > of your screen?
>>
>
> I wanted to resize to 1024x768. Not capture part of the screen.
>
> If you only want a segment of your desktop, you can let dshow capture
>> the complete 1366x768, and have ffmpeg crop the video to the part you
>> want to preserve. Insert (e.g.) "-vf crop=x=0:y=0:w=1024:h=768".
>
>
> Again, I don't want to crop it, however your suggestion reminded me of the
> scaling filter, I see there is -vf scale=1024:-1 The question I would have
> though is whether you believe filters create more work for ffmpeg or the
> computer as opposed to regular parameters such as -video_size? In other
> words, is a filter considered re-encoding where -video_size wouldn't be.
> Either way, I plan on testing with the filter.

Theoretically you could tell the capture filter to "downscale" it for
you, which...might save a little cpu.  I wouldn't imagine that
resizing is awful but I don't know how ffmpeg does it by default
(swscale has a lot of various sizing algorithms) so it's worth
profiling/benchmarking.

> Hi Roger,
>
>>
>> >   By default, it captures the "full screen" of the main desktop monitor
>> >   [...] To configure it differently, run the provided "configuration
>> >   setup utilities/shortcuts" or adjust registry settings before
>> >   starting a run (advanced users only) [...]
>>
>> I think it might respect video_size as well but I'm not certain, and
>> definitely not sure if it i truncates versus scaled or what not,
>> anyway you could try it.  Yes, I'm not sure and I wrote it  LOL, guess
>> it's been awhile.
>
>
> I noticed the code hasn't been updated in awhile on the git page. Have you
> stopped development?

Haven't worked on it in awhile.

> I'm curious, was the initial intention of you writing
> this program, a response of ffmpeg not having GDIgrab or disliking the
> results at the time?

If gdigrab had existed at the time I probably wouldn't have created
it.  Its initial impetus was that VLC couldn't capture screen + audio
at the same time (and possibly still can't LOL).

> If you disliked the results, would you say GDIgrab
> has improved?  Would you recommend using GDIgrab? Is that something that
> ffmpeg devs are consistently developing?

FFmpeg seems more efficient than other things I'd used, that's why I use it.

> And if so, is this why you've
> stopped development of screen capture recorder? My concern I suppose is
> will screen-capture-recorder be unusable as ffmpeg develops. Let me make it
> clear there is no judgement here either way, I just want to know for my own
> future development as I like the results of screen-capture-recorder.

I suppose the biggest danger is if windows changes its dshow stuff
altogether, which they haven't yet but who knows at some point.
Cheers!