BitPerfect: PCM Bit-Perfect Tester

[bronan]

Uploaded version 1.4 of the Test Kit. I finally got a new LD player and did some testing and was having trouble getting a bit perfect match. It turned out there were a few samples at the beginning and end that weren't matching up for one reason or another. I'm assuming it has something to do with the timing mechanisms of the player when it spins up and down, but I'm not sure yet.

Anyhow, I added a new feature to ignore a customizable percentage from the beginning and end of the reference, and it seems to have solved the problem. In my case I only needed to ignore the first and last 0.2%, which equated to a couple hundred ms on either end of the 52 second reference WAV. I also added more info on completion messages, so it will tell you how many continuous seconds matched on a successful one, or max matched bytes and index on a failed one (to help with debugging).

[spoRv]

Another way to test if a capture or audio card is bit-perfect is to grab a minute of the PCM track from a DTS laserdisc (that of course contains DTS), then de-encapsulate the WAV (or use a player that could understand that there is DTS inside that WAV file); if after few seconds sound will disappear/drift/turn to noise (I can't remember what happened, it was quite some time ago) then no bit-perfect.

The only downside is that a DTS laserdisc is needed...

[bronan]

The older version of this testkit used the DTS Parser program and a DTS audio file burnt to a CD. Its a black box though, and if something is wrong its not obvious what the problem is. That's why I've added features to this program like checking your exported WAV specs, checking for dual mono instead of stereo channels, etc. I hope to eventually get it running cross-platform as well for compatibility with all systems.

[bronan]

Been working on a port of the app to Avalonia, so it will be able to run on Windows, OSX, and Linux. Windows version is working now, and looks a little spiffier to boot. I am also going to add a couple more features, like being able to bit match a 24-bit recording to a 16-bit source.

https://i.imgur.com/1tfyc9N.png

[bronan]

I've rewritten a good portion of the testing logic, but it's now able to match 16-bit data contained in a 24-bit file to another 16-bit file. This could be useful for a couple reasons: 1) you don't have to export from Reaper anymore and can just use the raw 24-bit recording to do a quick Bit Perfect test (although I'd still recommend it at least once to make sure your export settings are OK). 2) You can try to match similar tracks from different BD releases if they're 16 and 24 bit. I've also exposed the detection to the UI with a new Info page which will tell you if any 24-bit PCM file contains only 16-bit data.

https://i.imgur.com/RTYOczN.png

[captainsolo]

Thanks for working on this further. I'm going to sit down and work on again trying to get bitperfect nailed down so I can finally start audio captures.

[bronan]

Just about done now with what will be version 2.0 of the app. All the features are done now, basically down to a little code cleanup and cross platform support. I've been going back and forth a bit with memory vs. speed when it comes to checking large files (500mb+). Streaming from disk takes virtually no memory, but its also way slower. Now that I have both options working I will do some real benchmarks and make a final decision. It would be nice for an option of either, but the code is different and more to maintain and bugs to worry about. After that I just need to make the OSX and Linux versions and test. If anyone is on those platforms and interested in helping please get in touch.

@captainsolo Just let me know if you need any help. I recently put together a new capture setup and ran into a few gotchas, so its still mostly fresh in my mind.

[spoRv]

I was thinking... isn't it possible to burn a CD and play it on any device that could play CDs with an optical output? In that way, one without a laserdisc player (yet) could always find if the audio card is bit-perfect or not - or just for the sake of knowing it!

[zoidberg]

lol spoRv, that was a few pages back I think

As I've said before, the 48kHz SPDIF output of a DVD player/cable box can also test for bit-perfect with either AC-3 or DTS. However to verify 44.1kHz then you will need LD DTS or a DTS audio CD, although I'd be surprised if an audio card was bit-perfect with one but not the other

[spoRv]

Well, as I do not remember what I did last day, it's a miracle my mind is working (more or less) well - sorta... yet...