atldotnet: ATL chapter implementation not displaying in Apple Podcasts and other podcast grabbers

The problem

While ATL does an amazing job of writing chapters in the correct CTOC frame in ID3v2 as per the Chapter Frame Addendum, now that the Apple Podcasts app has Chapter support, it’s a good test environment for ATL Chapter implementation; however, contrary to other podcasts that use a commercial chapter implementation, ATL Chapter implementation doesn’t seem to show at all in Apple Podcasts, and only partially shows in other podcast grabbers like Overcast.

Environment

• ATL version (or git revision) that exhibits the issue: 2.7
• Last ATL version that did not exhibit the issue (if applicable): N/A
• OS/version used to run ATL: Windows 10 x64, v1803, build 17134.648

Details

After inspection of the CTOC frame under Additional Fields for both implementations, the only notable difference is the lack of the ACKNOWLEDGE ACK (u0006) character, and the lack of the TIT2 sub-frame, which includes the START OF HEADING SOH (u0001) code, the UTF-16 BYTE ORDER MARK BOM (ÿþ)

commercial implementation:

{[CTOC, toc
CTOC
toc\0\u0003\u0006chp0\0chp1\0chp2\0chp3\0chp4\0chp5\0TIT2\0\0\0%\0\0\u0001ÿþT\0a\0b\0l\0e\0 \0o\0f\0 \0C\0o\0n\0t\0e\0n\0t\0s

ATL implementation:

{[CTOC, toc
CTOC
toc\0\u0003\u0003chp0\0chp1\0chp2

Note that for the commercial implementation after the UTF-16 BOM the string “Table of Contents” is concatenated

Steps To Reproduce Issue (images attached)

1. In Apple Podcasts iOS search the Ruminate podcast
2. Once located, play episode 13 “Crumpets On Your Tea Towel”, this specific episode contains a commercial chapters implementation
3. Scroll down and notice that under the Chapters section in the iOS app, there is a clickable Chapter list. Once clicked the podcast will be skipped to the beginning of each chapter.
4. In Apple Podcasts iOS, search the El Chilanyorker podcast
5. Once located, play any episode, all episodes in this specific podcast contain an ATL Chapter implementation

Result:

1. Scroll down and notice that there is no Chapters section in the iOS app, ergo no chapter list, and no clickable items.

Expected:

• The ATL Chapter implementation podcast should show the Chapter sections, a Chapter list, and chapter clickable items in the Apple Podcasts App

Note:

In the Overcast podcast grabber the same behavior happens, with a little exception: even when a Chapter section isn’t rendered, the Chapter titles do appear; however, there’s no way to navigate between them.

Thanks so much!