"Data error at XXX" when playing ALAC in current

[emody]

Hi,

I stumbled upon an error while playing alac files that affects the current builds and is not present in  version 3.13.
It's a deterministic error and does not happen in all alac files, just some of them. However, they will crash rockbox every time.
I see there were some commits in the alac part of the code since 3.13 related to playback/resume.

EDIT: I did a simple test. Taking the alac file that causes panics, I converted it to FLAC using ffmpeg. The FLAC plays correctly. I then converted this FLAC to ALAC using ffpmeg again, stripping cover art etc in the process. The resulting alac seems OK. It did crash right after copying but after a reboot of rockbox I'm unable to make it crash again. Will keep trying.

EDIT2: Well, seems it's unstable. At times I get solid lockup. No keys work. No screen updates.

If you need more information, I can help, but I have no knowledge in that part of the code.

emody.

PS: The reason for having a lot of alac files is that I share them with other Ipods

[saratoga]

The alac code hasn't changed since well before 3.13 so it is surprising that the version makes any difference. Can you post a link to the file and the exact device you're testing on?

[emody]

I'm running on Ipod Video (5.5g) with 30GB hd.  I was making a flash upgrade and lost a few hours before realising that I had the issue with the HD too.

When was 3.13 released ? Last mods in ALAC are around 2013 and they are post 3.13 but related to saving/restoring playback position. This is patchset 31b71228

Something suspicious could be patchset 3fd25dcb on 2013-05-05, a couple of months after 3.13 was released.

I'll post you a PM with the file as it's (C) music. Not sure I can post it here in the wild.

[saratoga]

3.13 was released in 2013.  There have been zero changes to the ALAC decoder since then.  alac.c has one change that you noted, but it is non-functional (renames a variable without changing its value). 

Send me the file, I'll try and look at it in a few days when I am home. 

[emody]

Agreed, let me double check that I have no issue at my side so I don't waste your time.

[emody]

Ok, I did some more testing. It appears that the issue is not "easy" to reproduce. I copied one alac file in a new directory and it started playing correctly. It would not play correctly in the original directory (I checked the md5 hashes and they match).

I tought that it might be somewhere in the disk reading/caching code, so I added one more song to the new directory and the cover.jpg file and voila! I can make it crash now, but not always. You need to turn rockbox off, then on again and go to the new directory and play the file.

Every so often it willl crash with "data error".

I'm attaching a screenshot of one of these errors. The addresses change slightly when you move files / rename them etc, but they're are in the same "region", few bytes apart. I'm not sure if these can be mapped to the actual code or if rockbox O.S. has dynamic allocation of code.

EDIT: I tried to just replace .rockbox between 3.13 and dev. 3.13 still plays correctly the same file.

[emody]

Saratoga, I sent you a PM with a link to the files. Pls tell me when you downloaded them so I can take them offline.

On a side note, I upgraded my ipod with a iflash solo and a 128GB sandisk ultra. It was tested with h2testw beforehand just in case and passed.

I have the same issue as with the HD now, same file same address.

I'm waiting for a batch to complete for converting all my alac to flac just for rockbox but I'll lurk this thread in case I can help further.

emody.

[saratoga]

Thanks, I got those files.

They play fine for me though.  Do I have to do anything special to make them crash? 

[emody]

Not really. I'm using a skin (AluminArt) but the problem is there also with the default calliev2. I'm under the impression that the issue is disk access (errors or timing?). The first file will crash at the beginning. Try clearing your database and force regeneration in background during playback.

A side note: Is there a way to debug rockbox in the target? Or a way to know where those addresses are ? It should be possible to match that agains the linker map for a clue.

[saratoga]

These crashes happened with the original hard drive right? Hard disk corruption is pretty commonly reported with SD card adapters.

If you compiled your build you can look at the .map file included in the build directory to see where those addresses are.

[emody]

Well, it happens on both hard disk and a flash adapter. If I copy the file from the ipod to my local disk, then copy this file from my disk to another directory in the ipod, it will break at the same point.

I'll compile my own and see where that address is. This might be related to an issue of my ipod off course. The fact that on the same hard disk and flash adapter the old 3.13 works while dev does not is indicative of something more than just that-file-is-corrupted or that-directory-is-corrupted.

Will let you know as soon as I have the build going.