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View Full Version : mplayer audio playback of tystream from OTA DTV



bcc
06-13-2004, 12:37 AM
I found that mplayer (1.0pre4) is unable to play back mpeg2 audio tracks in OTA recordings made by hr10-250s (AC3 audio works OK). This in turn is due to the assumptions mplayer is making about the audio packet lengths. (mplayer is throwing out the audio because the length is not as expected). I have hacked mplayer to fix this, and it's now working "fine" for HD OTA recordings.

Anyone want to play with these changes/help?

bcc
06-13-2004, 01:00 PM
Update: I've fixed things so that SD audio plays back as well. In my test case, the SD audio (AC3) spans packets, and mplayer was not reassembling the data correctly.

redstone
07-14-2004, 05:58 PM
Sorry, I just spotted this post.

Where is this version that you have made?

The version that I found is on mplayerhq.hu

Is this the one that you modified?
It plays OTA HD recordings (the one I have for testing) okay.

bcc
07-15-2004, 03:44 AM
Where is this version that you have made?Nobody expressed any interest so the changes haven't gone anywhere yet. The source code diffs for 1.0pre4 are enclosed below. I should have clarified in my original message that the problem case is mpeg2 audio not AC3 audio. In my test cases no HD OTA mpeg2 audio has played at all but AC3 audio has. For example, law&order is AC3 audio so it was OK. Jay Leno is mpeg2 audio so mplayer wouldn't recognize it, printing "Audio: no sound". You probably have only tried AC3.

There are basically 2 parts to the diff - fixing mpeg audio to check for a PES header, and generalizing the audio header processing so that ac3&mpeg2 share the same code. The later required fixing mplayer's idea of the AC3 PES header length. Without fixing that length as well, AC3 audio frames that span multiple PES packets would not reassemble correctly.