Crash when this particular mp3 finishes playing

SDK Bug Reports
1

E3M6_vbr_48.mp3.zip (909.8 KB)

Encoded by Audacity as mp3, forced mono, vbr 48 kbps

  • When trimmed to 5 seconds no crash occurs

  • when converted to CBR, no crash occurs

  • Only on hardware, on simulator it finishes fine

        self.player = playdate.sound.fileplayer.new("music/E3M6_vbr_48.mp3", 2)
        self.player:setStopOnUnderrun(false)
        self.player:setVolume(self.volume)
        self.player:play()

Error accessing buffer at 0x60143636

2

Found it. The problem is the end of the file has some frames that are smaller than the 38 byte minimum I'd assumed, which leads to us trying to read a negative number of bytes off the disk. In the simulator that's ignored (I think?) but on the device it's passed unsigned, which means it tries to read ~4GB of data and overflows the buffer. Oops. :frowning: We should push the extra bytes back to the buffer instead.

The LAME encoder has a minimum bitrate flag that would probably work around this, but I don't see any way to use that in Audacity.. But it looks like trimming the silence at the end of the file will keep this from happening until I get the bug fixed. After cutting it back to 2m54.8s and re-exporting I don't see any short frames. Or you can just trim the original mp3, looks like the first short frame is at offset 0xE6B9C:
E3M6_vbr_48-trimmed.mp3.zip (909.6 KB)

1 Like
3

Marking as solution since there are many workarounds. I'd consider this low prio

1 Like
4

@dave Re-opening this issue because the inverse has now occurred:

The attached 32kbps abr (average bitrate) MP3

  • plays fine on hardware using firmware 1.13.0 beta6
  • crashes simulator 1.12.3 immediately on playback.

As before, choosing CBR as an encoding parameter works on both simulator and hardware. I'd much prefer ABR though, because it has a smaller filesize for comparable quality

I have used the option in the simulator to send a crash report to Panic.
Note: I have erroneously reported there that it was encoded as VBR, while in fact it is ABR (average bitrate)

director_intro_2_vbr_simulator_crash.mp3.zip (57.7 KB)

5

1.12.3 had a bug in the mp3 decoder where a frame smaller than 38 bytes causes a negative read length, which then crashes. I'll DM you a 1.13.0b6 simulator build. What platform are you on?

6

Thanks. I'm on MacOS Intel