[mythtv-users] Audio distortion watching some recordings and videos

[Brad DerManouelian]

On Oct 12, 2006, at 7:48 AM, Jerry Bett wrote:

> On 10/12/06, Dawson, Guy <Guy.Dawson at eu.sony.com> wrote:
>>
>>
>> Hi
>>
>> I've been running 0.18.1 on FC3 for a while now,  and have not  
>> noticed any
>> audio problems until recently.
>>
>> It's hard to describe,  but it sounds a bit like the faint  
>> twittering of a
>> large number of small birds, or perhaps crickets. It only happens  
>> in certain
>> passages.  I first noticed it above some canned laughter during a  
>> transcoded
>> recording of a UK TV sit com (shame prevents disclosure).   
>> Subsequently,
>> I've noticed it over high pitched vocals and during otherwise  
>> quiet passages
>> of a divX of an American TV show, viewed with mplayer.
>>
>> Does this sound familiar to any one?  Failing that, any pointers  
>> as to how
>> to go about isolating the problem?
>>
>> Thanks in advance
>>
>>
>> Guy Dawson
>>
>>
>
> Guy,
>
> I've noticed distortion on some of my recordings ... though to me it
> sounds more like a 'swishing' sound.  I can get the same sound doing
> mp3 only recordings...and the lower the bitrate, the more distortion I
> can hear.
>
> I wonder if you might try increasing the transcoded bitrate of the
> audio and see if that mitigates the problem ?
>
> Jerry

This does sound like mp3 compression artifacts. I hear the same thing  
in AAC and MP3 with certain frequencies with a sustainable length  
(like a cymbal crash or in your case canned laughter). I long for the  
day where disk space and bandwidth is no longer a consideration and  
we can enjoy full uncompressed video and audio.