[FFmpeg-user] Picture jerky when screencasting?

[lugoteehalt]

belcampo wrote:
> 
> On 06/02/11 00:25, lugoteehalt wrote:
>>
>> belcampo wrote:
>>>
>>>
>>> I don't know what ultimately your intention is, but you're playing
>>> iplayer, which is 25fps, so grabbing at -r 30, isn't .... AFAIK
>>> You've choosen lossles which results in 1002700kb/s which is an awfull
>>> lot of data to process.
>>> Your system also has to decode and display the iplayer stuff, don't know
>>> how taxing that is on your system, but all in all I think it's way too
>>> much for any system. I'm not 100% sure though.
> To place some things in perspective:
> You've choosen lossles which results in 1002700kb/s which is an awfull
> lot of data to process.
> 1002700kb/s is 1Gb/s Only the fastest single desktop disks can be 
> written to at that speed. The average modern non-laptop disk does 
> between 80MB/s and 175MB/s. So only the fastest desktop-disks g\could 
> theoratically do that. The average laptop-disk can do between 30MB/s and 
> 60MB/s, the fastest can only accept half, and that is theoratically, of 
> what you are trying to capture. Capturing non compressed video like 
> iPlayer at 720p is more or less 'impossible'. But I like to be proven
> wrong.
>>>>
> 
Thanks.

Intel Celeron C900, single core presumably. 2GB RAM.  Cheap laptop. 

Have got it vaughly working.  It is still webcammy on iplayer fullscreen,
not on non-fullscreen.  But the webcammyness is almost acceptable.  The
command is:

ffmpeg -f alsa -ac 2 -i pulse -f x11grab -s cif -r 25 -s `xdpyinfo | grep
'dimensions:'| awk '{print $2}'` -i :0.0 ~/out.mpg

The file for 3 mins, about 1/2 min at iplayer fullscreen, has size: 
video:21370kB audio:1504kB global headers:0kB muxing overhead 0.550217%

Would not object to a much bigger, say 10x, file if it got less webcammy. 
Assume it could be compressed at leasure later.


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