Hi Romain,

Thanks for this. I will test this at weekend.

One more question for the remaining 1% :
qwavheaderdump supports fixing track length by parameter -f: qwavheaderdump -F 
'$filename'

Filenames are generic by using  reopen_when() with "|%SMHdmY|" syntax.
I would like to start an external qwavheaderdump -F call at stop of each 
recording, but would need to pass the filename to this.
Is there a way to use the right filename at on_stop() function?

BR, Peter



Am 04.08.2011 06:11, schrieb Romain Beauxis:
> 2011/8/3 Peter Retep<[email protected]>:
>> Hi Romain,
> Hi!
>
>> Thanks for this fast answer!
>>
>> 1)
>> Approach 1 should help in 99% cases and would fit to our usage, btu the
>> length of the first file will not be correct using this.
> I have just committed this.
>
>> But how do you thing about predicting file length by "next reopen_when()
>> event time" - "now()" ?
>> This prevents using an additional parameter and furthermore the length of
>> the first written file will be okay.
> This is insteresting. However, I dont know about adding a parameter
> whose meaning would be mostly intended for one particular format.. We
> actually moved to %foo encoders partly to get rid of those issues..
>
> I also think that with some efforts, it is totally possible to emulate
> this by using dynamic sources.
>
>> 2)
>> Since we are recording from ALSA there is no metadata, which makes approach
>> 2 not helpful to us.
> Word.
>
>> 3)
>> A more generic solution could happen after the last write to a WAV file:
>> if you know frequency, bitrate, number of channels and size of file and size
>> of header you could update the length field by
>> length = (file_size - header_size ) / (2 channels * 16 bit * 44100 bit/sec)
> The problem with this is that we may not always have the possibility
> to rewind the stream. The output could be /dev/null or stdout and we
> actually do care about the latter...
>
>> 1) and 3) could be combined:
>> - at start of recording file length could be predicted by reopen_when() or
>> by length parameter.
>> - at end of recording file length can be quickly measured and updated if not
>> matching.
>> This combination could make LS robust for writing WAVs at most start/stop
>> cases (except LS process killing).
> I think we'll have to stick with 1) for the moment.. Please let me
> know if the changes are helpful to you..
>
> Romain
>


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