Sample rate issue


(Oliv Rougeot) #1

Hi,
I am confronted to a strange issue.
I opened a session at 48 k then record my audio and had several takes until here everything is ok .
Then I consolidated the intervals to get rid of useless audio ( and as I am always rushing, cleaned the session ) and then audio could not be heard .
So no worry, closed the session, rebooted the PC and … Ok audio is back but you know …, with the Donald Duck’s syndrome.
All the files seem to be resampled in 44,1 . So if I open the session properly : no good ,but if I force it to open in 44.1 then it sounds ok.
If someone has an idea.
By the way I have already been confronted with this when someone recorded a session ( I don’t remember the name of Ardour’s equivalent for live sessions) with it and it was in 48 k but when I tried to open the files I had to read them in 44.1…
If someone has a clue.
Olivier


(Len) #2

I don’t know windows audio well, but this could be a hardware issue. If the audio interface is opened at a rate that the device doesn’t offer or the device is synced externally, it could seem to be at 48k when it is actually running at 44k1. Now in your case the device can do 48k, but it seems while recording it is not. Ardour runs from the devices clock rate (interrupts) and so if the actual rate on the card is not what was asked for, Ardour does not know. For example, if you are using a spdif input module to your sound card or adat to sound card, it could be that the adat or spdif module is acting as master clock and is set to 44k1. Anyway, just a guess.


(Oliv Rougeot) #3

Hi,
Thanks,
Well I don’t think so .
I have an internal card as master clock and external converters seem to follow it well ,
It really seems that there is a change inside the files ,
If I try to open them in an audio editor the sample rate is wrong but by changing the hardware sample rate ( what I call " force Ardour to open in 44.1") then they sound ok.


(Oliv Rougeot) #4

Well ,sorry,sorry !
I guess you are right . It must be hardware related !!!
I don’t know what I am doing ,but I DO a thing which makes Ardour think that audio should be coded in 44.1and read in48 ( meaning files are unusuable)
It must be related with Windows sound device assignation : meaning ,If I use the Ardour’s audio card as the default Windows device ,It makes a mess somewhere…
If I understand what I am doing wrong, I will let you know.
Edit : By the way ,the audio recorded at 48k was ok , the issue occured after I " reduced" ( consolidate) the layers,ie somewhat after some kind of edit .


(Len) #5

The reason I picked HW is that it was on restarting that the problem showed up. So on recording Ardour asked for 48K but for some reason (again I don’t know windows) either a sync issue with the HW itself or another program was using the device at 44k1 and had it locked there, the windows audio system did not change the rate to 48k and was running at 44k1. When your session crashed and you had to restart, Ardour again asked for 48K and because whatever condition caused the false rate the first time was no longer there, the device did change to 48k and sounded wrong. So in effect the wave file that have your tracks in them were recorded at 44k1 but are labeled as 48k. It seems to me it would be a good idea for Ardour to report an error if the timing of interrupts does not line up quite close to the requested rate.


(Oliv Rougeot) #6

Hi Len
Thanks,
I guess I opened something and did not Check the master clock sample rate .
The only thing is that I don’t understand why Ardour did not see It.
I don’t remember exactly but I think that generally in this kind of situation,there is an alert saying :" the soundcard is not set at the right sample rate "