[mythtv-users] Closed Captions: A reason to upgrade?

[faginbagin]

On 6/5/2011 2:19 AM, Michael T. Dean wrote:
> On 06/05/2011 01:33 AM, faginbagin wrote:
>> I'm currently running 0.23.1-fixes on my MBE/FE and 4 FEs and have been happy with it. However, my service provider, Wide Open West (aka WOW), is in the process of going all digital, and after phase 1 of their cut over, I find that MythTV is unable to display closed captions on some, but not all, of the std def digital channels. Closed captions are there, as verified by viewing the same channels on my HDTV and recording them on MythTV at the same time. I have tried both EIA-608 and EIA-708 captions, but no joy. So, I thought I'd ask if this is a known problem in 0.23.1-fixes that's fixed in 0.24 or later.
>
> There were quite a few fixes to EIA-708 captions for 0.24.  This is not
> meant to be assurance that upgrading will help with this particular
> issue, but it's possible it may.
>
> Mike

Thanks for the honest answer. Based on Alex's experience, I'm going to hold off on upgrading.

As it happens, I have the means to test some of MythTV's code that involved with decoding of EIA-608/708 data without using the internal player. Quite a while back, I wrote a program I use to convert EIA-608 data (and ivtv's vbi data and nuv's text frames) into DVD subtitles. It has a tweaked copy of AvFormatDecoder::DecodeDTVCC (copied from /libs/libmythtv/avformatdecoder.cpp). The executable is linked with Myth's versions of the ffmpeg libraries. I finally got around to using this program to take a closer look at a recording that should have some form of CCs. I think I can safely say that the problem is in the ffmpeg libraries, probably libs/libavcodec/mpeg12.c's function: mpeg_decode_user_data

I have only spent a couple hours on this (capturing a couple of recordings at the same time I see CCs on my HDTV, executing my utility with verbose logging and then skimming through 0.23.1 code), so I could be way off base. But maybe this skimpy info from an old version will be of help to Jim. Time permitting, I think I'll see what's changed in the trunk version of myth's ffmpeg libraries, and maybe poke around the latest ffmpeg source, too.

Thanks,
Helen