[Audacity-devel] A problem found?

[Martyn S. <mar...@gm...>]

Hi

As a result of a user problem forwarded to me by Gale, I have found a 
reproducible way of getting the sort of data loss that some users are 
experiencing when moving from 1.2.6 to recent builds.

Try this:
Open 1.2.6
Project -> New Audio Track
Set Sample Format -> 16-bit (sampleformat="131073" as an attribute of 
'sequence' in a project file)
Generate -> White Noise (for example) -> 20s
File -> Save Project as 'test'
Open test.aup in a text editor
Note that you have
<sequence maxsamples="262144" sampleformat="131073" numsamples="882000" >
	<waveblock start="0" >
		<simpleblockfile filename='b00000.au' len='524288' min='-1.000000' 
max='1.000000' rms='0.576815'/>
	</waveblock>
	<waveblock start="524288" >
		<simpleblockfile filename='b00001.au' len='357712' min='-1.000000' 
max='1.000000' rms='0.551214'/>
	</waveblock>
</sequence>

The simpleblockfiles are of length 524288 and 357712 whereas 'sequence 
maxsamples="262144"'.  This causes the problems that we have 
seen/discussed recently, reading them in to 1.3.X.  It also happens 
for 16-bit stereo files.

More weirdness!  Duplicate the track and then set it's Format to 
32-bit and Save Project.  File sizes in test_data are now about 2MB, 
maxsamples for the second track has changed to "524288" (which is now 
illegal for sampleformat="262159" (floatSample), since that would make 
the file too big (int Sequence::sMaxDiskBlockSize = 1048576;) I  believe.

I believe that there are a number of bugs in 1.2.6 that are causing 
this, including ignoring maxsamples when reading the files in.

If I am correct (and I haven't always been before ;-)) then we should 
do our best to read older stuff into our current version.

This seems like progress to me!

TTFN
Martyn