[pvrusb2] Re: xawtv recording?

[Mike Isely]

On Wed, 9 Nov 2005, Simon Lachinger wrote:

>> --- Ursprüngliche Nachricht ---
>> Von: Frans Meulenbroeks <fransmeulenbroeks at yahoo.com>
>> An: pvrusb2 at isely.net
>> Betreff: [pvrusb2] Re: xawtv recording?
>> Datum: Tue, 8 Nov 2005 23:12:15 -0800 (PST)
>>
>>
>>> For recording, all you really have to do is:
>>>
>>> $ cat /dev/v4l/video0 > recorded.mpg
>>
>> Note that this only works to a certain size.
>> On my 2.6.14 kernel this stopped after scribbling 2 GB
>> (which is in the default settting of 6 Mbit/s less
>> than 1 hr of video). So this is ok for a short show,
>> but not for a movie (unless you want to give up
>> quality).
>>
>> Frans
>>
>
> That way I've recorded whole films each with a file size way beyond 2GB.
> What file system did you use? The 2GB boundary sounds strangely familiar to
> me (VFAT?)..
>

2GB is the single file size limit you will encounter for ANY file system 
when using 32 bit file access semantics.  If, for example, your app 
depends on using lseek(), that function uses a 32 bit pointer which limits 
you to 2GB (well, 4GB, but file offsets have traditionally been signed 
ints, which gives you only 31 bits or 2GB of addressing range).  There is 
another call (llseek()?  not sure..) which uses a 64 bit pointer and thus 
avoids the limit.  So it may not matter at all what the underlying file 
system is, if the app is using system calls which can't get past 32 bits 
of addressing.  I wouldn't be surprised if the apparent conflicting 
answers here might be due to xawtv being configured differently in each 
case.  Check your config step results - there may be something there which 
enables the use of 64 bit addressed file I/O.  Note: This is wild 
speculation; I have no special experience about xawtv which would tell me 
that this is the root cause, and under NO circumstance am I volunteering 
here to start trying to support big sticky ball of mud otherwise known as 
xawtv :-)

   -Mike


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