[linux-audio-user] upsampling wav's - ardour sessions

MarC marc_contrib at ramonvinyes.es
Sat Feb 26 12:52:41 EST 2005

En/na R Parker ha escrit:

>--- MarC <marc_contrib at ramonvinyes.es> wrote:
>>I'm using ardour to record and I have recorded my
>>songs at 44100 until 
>>now. Now I want to switch to 48000.
>>What's the easiest way (always within the best way
>>to do it) to convert 
>>my sessions to 48000?
>>I would like something automatic like running a
>>script before starting 
>>an ardour session at 44100 or clicking some option
>>at ardour to import it.
>>I have googled this issue and I found:
>I'm curious why you want to switch. The only practicle
>reason I can think of is that your hardware runs at
>48000 and a conversion has to take place on the fly so
>you're trying to improve computational effiency.
well the reason is a JACK bug which nobody seems to know how to solve. 
Moreover, I think that Audigy runs at 48k so it may improve 
computational efficiency or make it perform better... but it isn't the 
main reason.

Then sbdy of the jack list has told me that with 48000, the problem 
disappears, so that's why I may need to resample.

I quote here what I sent to the jack-devel list:

I don't know whether this is a bug or not.
I have a P4, 512Mb RAM, and an Audigy. I configured JACK for a latency 
of 11ms, realtime, and I have a debian-testing GNU/Linux with 
kernel-multimedia-2.6.10 (from http://apt.agnula.org/demudi/)

Then, if I start xmms with jack and play some songs, everything runs 
alright in the first minutes but after some time I always start hearing 
an annoying noise which prevents me to use ardour to play live.

(I have recorded it and you can download it at 
NOTE: you will see that the noise only is present when there is a sound, 
as when there is the silence between two tracks, you can't hear it)
NOTE2: when working with ardour, if I'm recording the sound of a mic, 
even if I hear this noise at the final output, the mic is well recorded, 
so this noise only affects the PCM output...
NOTE3: when I use alsa, I never have this problem.

After a while this noise disappears without doing anything and in the 
message window of qjackqtl I get:
**** alsa_pcm: xrun of at least 0.099 msecs
18:27:46.204 XRUN callback (1 skipped).

If I configure JACK for higher latency, this noise appears later but I 
can't get rid of it.
Maybe Audigy doesn't allow these latencies and this is "a normal XRUN". 
However I can't understand why JACK doesn't reset before and I must hear 
all this annoying noise until it stops during a minute. In fact, if I 
change the latency without shutting down JACK with ardour, the noise 
disappears but I can't do this manually while recording and I think JACK 
should do the reset for me...

>You've already got libsndfile installed which includes
>sndfile-resample. I'm not sure if you can convert the
>rates, start jack at the new rate and open the Ardour
>session without having Ardour complain.
well. In fact, ardour *complains* with warnings. How can I avoid it?
The result is that the song is read at a different speed+pitch because 
it was recorded as 44100 and now it is played at 48000. I can't 
understand what do you mean.

> In theory it
>makes sense that you can because Ardour shouldn't care
>about samplerate. It should look at jackd for the
>currently running rate and examine the files to see
>what rate they are. If they are the same, open session
>and run. I guess you'll need to test that.
>>but it's not debian-packaged yet and I'm too lazy
>>maybe ecasound? but I'm afraid it doesn't consider
>>so much things as 

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