[mythtv-users] Underwater audio

Gregorio Gervasio, Jr. gtgj at pacbell.net
Fri Feb 29 09:18:43 UTC 2008


>>>>> Michael T Dean writes:

m> On 02/28/2008 07:10 PM, Curtis Stanford wrote:

>>> I think I have the same problem with 32kHz audio in NUV recordings
>>> (framegrabber). The patch in this ticket (reverts some rev 15893
>>> changes) seems to fix the problem for me:
>>> 
>>> http://svn.mythtv.org/trac/ticket/4764

>> That totally fixed my problem. Thank you!

m> Would be /really/ nice is some of you could test the value that's being 
m> changed by that patch and find the smallest value that works...  Try 
m> starting at 120000.  See: 
m> http://www.gossamer-threads.com/lists/mythtv/dev/319315#319315


        Based on limited testing, it's "fragment_size" rather than
"buffer_time" that's affecting this specific "underwater" problem:

1. (rev 15893)
   fragment_size = (audio_bits * audio_channels * audio_samplerate) / (8*30);
   buffer_time = 100000;
-> BAD -- underwater effect

2. (pre 15893)
   fragment_size = 6144;
   buffer_time = 500000;
-> OKAY

3.
   fragment_size = (audio_bits * audio_channels * audio_samplerate) / (8*30);
   buffer_time = 120000;
-> BAD -- underwater effect

4.
   fragment_size = (audio_bits * audio_channels * audio_samplerate) / (8*30);
   buffer_time = 500000;
-> BAD -- underwater effect

5.
   fragment_size = 6144;
   buffer_time = 100000;
-> better -- sounds okay but audio is sometimes lost when skipping
around (need to exit and restart)

6.
   fragment_size = 6144;
   buffer_time = 120000;
-> OKAY

        I will try out this last setting for a while.
-- 
Gregorio Gervasio, Jr.


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