2011/8/2 Peter Retep <[email protected]>:
> Hi,
Hi Peter!
> as mentioned at ON2 last year we have problems with post processing of WAV
> output.
> Anyway, now I have found time to see, what is wrong with this:
> It seems that length is not encoded in the right way.
I confirm the issue.. The problem is that the WAV header is written
first and, when writting on-the-fly, total duration may not be known
at the time the header is written..
I am not sure that we can do much about this to actually reflects the
exact length of exported data. However, I can think of at least two
workarounds:
* Add an optional length parameter to %wav encoder. If the duration
of the files you will encode if known in advance, you could set it to
this value
* Use the "duration" metadata if available. This would only work for
encoding of files and could be tricky if the resulting files contains
several songs..
I think the first one is the only reasonable option. Could it fit your needs?
> If you use WAVs recrded with LS for postprocessing like cutting it and encode
> it with lame,
> lame (3.98.4) will still copy this length field, a lot of media players will
> show the wrong length then.
>
> I have used qwavheaderdump (from the quelcom package) to check wav.
>
> qwavheaderdump 2011-08-02-00_00_00.wav
> 2011-08-02-00_00_00.wav (635054156 bytes):
> riff: 'RIFF'
> riff length: -268435457
> riff length field should be 635054148
> wave: 'WAVE'
> fmt: 'fmt '
> fmt length: 16
> format: 1
> channels: 2
> sample rate: 44100
> bytes/second: 176400
> bytes/sample: 4
> bits/sample: 16
> data: 'data'
> data length: -268435493
> data length field should be 635054112
>
> As a workaround one can use following command to fix teh WAV header.
> qwavheaderdump -F file.wav
>
> my encode settings:
>
> output.file(
> %wav(stereo=true),
> "/mnt/archive/piradio/%Y-%m-%d/%Y-%m-%d-%H_%M_%S.wav",
> reopen_when={0m0s},
> mksafe(radio)
> )
>
> my (still old) liquidsoap version as used in the production system:
>
> Liquidsoap 1.0.0-beta+svn (trunk/liquidsoap@rev8193).
> Copyright (c) 2003-2010 Savonet team
> Liquidsoap is open-source software, released under GNU General Public License.
> See <http://savonet.sf.net> for more information.
>
> Please confirm and I will create a ticket for this.
>
>
> It's the same for a nearly current release:
>
> Liquidsoap 1.0.0-beta2+svn (@644dd3b27614:20110706:175811)
> Copyright (c) 2003-2011 Savonet team
> Liquidsoap is open-source software, released under GNU General Public License.
> See <http://savonet.sf.net> for more information.
>
> quick test:
> liquidsoap 'output.file( %wav(stereo=true), "./test_%M.wav",
> reopen_when={0s}, mksafe(noise()) )'
>
> BTW: When using 'reopen_when={0s}' LS will not create a separate file for
> each minute.
This is probably due to the fact that 0s is too tight and that the
test is run for instance at 1s. Although, I think the test is executed
at each frame which by default is 0.04s I think..
The solution, I believe, is to use a wider range, something like: { 0-59s }
In this case and in order to avoid several reload withing the same
minute, the reload_delay prevents any reopening for the given duration
in seconds after the first reopening..
Please, let us know if the above works for you..
Romain
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