[mythtv] Bad sounding audio

Mark Spieth mark at digivation.com.au
Mon Aug 12 23:11:12 UTC 2013


> 1. audio sounds distorted. I understand this is now fixed since 
> yesterday. will update and test again tonight. upmixer on or off 
> doesnt matter.
> 2. audio sounds mono even though logs say its not. this includes HD 
> broadcasts. Very puzzling. happened in the last 2 months. upmixer on 
> or off doesnt matter. 
I have some clues on these now. Audio samples in 
AvFormatDecoder::ProcessAudioPacket just when AddData is called show

0x35d3400:      0xedf5  0xba6b  0xe9c4  0xba9a  0x1aa8  0xba7d 0xa3fa  
0xba99
0x35d3410:      0xd891  0xba86  0xfdda  0xba98  0xb77f  0xba87 0xeaa0  
0xbaa4
0x35d3420:      0x9ac9  0xba7d  0x9de2  0xba9d  0x8fb5  0xba38 0x507c  
0xba61
0x35d3430:      0x5953  0xb9b2  0x295a  0xba06  0x1ecf  0xb989 0x31e4  
0xb9f5
0x35d3440:      0xd058  0xb9bc  0xf55b  0xba09  0x7247  0xb8e5 0xf042  
0xb98d
0x35d3450:      0x108f  0x39ca  0x6257  0x395c  0x5b8e  0x3a2f 0xa8b4  
0x3a0a
0x35d3460:      0x3d52  0x3a46  0x29e7  0x3a1f  0x2625  0x3a21 0x83e2  
0x39e4
0x35d3470:      0x26ab  0x38e0  0xef16  0xb781  0x19d0  0xb959 0xaf17  
0xb9a1
0x35d3480:      0xe30a  0x38a1  0x729e  0xb8ca  0x131f  0x3981 0x8e5f  
0x38be
0x35d3490:      0x6213  0xb7d1  0xc075  0xb8cb  0xb77f  0x38de 0xc9e2  
0xb713
0x35d34a0:      0x7274  0x3a57  0x1d1a  0x3a28  0x1f81  0x3a9e 0x7e39  
0x3a8e
0x35d34b0:      0xf9cd  0x3a82  0xfa6f  0x3a72  0x1cfa  0x3a4d 0x51a3  
0x3a2a
0x35d34c0:      0x22ab  0x3a3b  0xff8f  0x3a0e  0x6f95  0x3a06 0xef49  
0x39cb
0x35d34d0:      0x089a  0x394b  0xd1b1  0x38d2  0x20de  0x3878 0x7ac4  
0xb89c
0x35d34e0:      0x4830  0x396c  0x59da  0x3827  0xf84b  0x39d7 0xba84  
0x3986
0x35d34f0:      0xd55c  0x39cc  0x7259  0x3997  0xc98f  0x39dd 0x375d  
0x398a
0x35d3500:      0x9369  0x3a36  0x4dc0  0x39f4  0x08eb  0x3a66 0x62d2  
0x3a39
0x35d3510:      0x1711  0x3a5f  0xa0db  0x3a3c  0x73fe  0x3a75 0x310d  
0x3a3b
0x35d3520:      0xe744  0x3a86  0x7b41  0x3a4b  0x7805  0x3a3c 0x7cc0  
0x3a0a
0x35d3530:      0x2689  0x393c  0xaeff  0xb804  0x429a  0xb885 0x296d  
0xb9ad
0x35d3540:      0x59ca  0x38f3  0x07ff  0xb911  0x8c19  0x39dd 0x835e  
0x3926
0x35d3550:      0x313f  0x3a07  0xa19d  0x396d  0xa582  0x39d4 0xbe42  
0x3913
0x35d3560:      0x22e2  0x39da  0x164d  0x38fb  0xc131  0x3a11 0x0b77  
0x394e
0x35d3570:      0xe8cc  0x3a14  0xa99e  0x398a  0x8c72  0x3a19 0x571d  
0x39a3
0x35d3580:      0x34d6  0x3a3d  0xca95  0x39af  0xc296  0x3a1e 0x1971  
0x395e
0x35d3590:      0x7821  0x3987  0x777e  0xb7e5  0x6a96  0x3911 0xbec8  
0xb955
0x35d35a0:      0xaf72  0xb741  0x0808  0xb9ee  0x9f3f  0xba28 0xfcb2  
0xba82
0x35d35b0:      0x05c6  0xbaa3  0x90b0  0xbacb  0xfdef  0xbaaa 0x4e22  
0xbae1
0x35d35c0:      0x0037  0xba97  0xdd76  0xbacc  0x1e60  0xba6d 0xdff5  
0xbaa0
0x35d35d0:      0x61cd  0xb9b4  0xa444  0xba39  0xfaba  0x3915 0x3b0b  
0xb98b
0x35d35e0:      0x6b92  0x38e8  0xd743  0xb974  0xf897  0xb934 0xfdb1  
0xba03
0x35d35f0:      0x6aa1  0xb9e7  0x7578  0xba54  0x3388  0xba4e 0x4c4d  
0xba93

Notice how the odd cols (right ch) are all in 0x38XX and 0xbaXX region. 
Looks like a square wave with a bit of ripple
Left ch looks fine..
must be a bug in libav.
This is with AAC but it looks like it happens for AC3 and MP2 too. must 
be something common.
perhaps FFMPEG resync issue.

Ill start a ticket later with this stuff unless someone beats me to it.
more tonight.

mark


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