Rockbox

Do your files play gaplessly in other audio players (e.g. foobar) ?
Did they play gaplessly in earlier version of Rockbox?
Do you have any unusual tags in the files, e.g. APE?
Are you playing the files continuously from beginning to end, or are you seeking in them?

I played the same file in earlier version of Rockbox svn rev-12322.
This version can play with gapless.

Can you try some of the other recent daily builds for the 5g and see which (if any) was the last one to play your files gaplessly? You can download them from here:

http://www.rockbox.org/dl.cgi?bin=ipodvideo

Are you also able to upload to somewhere a pair of test files that played gaplessly in previous versions of Rockbox, but don’t any more?

I try recent daily builds (r12343-070217) for the 5g.
But this version is not able to play gaplessly.

I attach a pair of test files.
This file can play gaplessly in foobar2k and rockbox rev-12322.

   001 WAVE00.mp3 (234.7 KiB)
   002 WAVE01.mp3 (234.8 KiB)

I made a patch that delete SWCODEC check.
I can play gaplessly with this patch.

   del-SWCODEC_check.patch (1.4 KiB)

I have committed a fix for this. Thanks for reporting and helping me see the bad spelling of CONFIG_CODEC. Please test the next build and tell me if it works.

It works fine :)