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SM 2.46 browser, MP3 audio decoding extreme distortion

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webmoebius
 
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Joined: January 21st, 2007, 12:52 pm

Post Posted May 2nd, 2017, 3:45 am

Frank Lion wrote:The 'player' is internal and the problem is caused by it trying to force stereo decoding on a mono source. Luckily, the solution is a simple one -

Put about:config in the addressbar and press Enter. Right click any entry in the about:config window and select New > Boolean and put this as the entry - media.forcestereo.enabled and make sure that it is selected as false. This only needs doing once.

Refresh your audio page and your problem will be gone...as if by magic.


I didn't realize this thread had developed this much since I last visited the forum. Sounds like you've nailed the problem on the head. Just to be sure, would this parameter switch affect MP3 decoding that is originally stereo? I would assume the answer is NO, since your explanation suggests that the problem arose only due to stereo decoding forced on a mono source clip. I just want to be sure before I add this parameter, as I haven't figured out a way to delete manually added parameters in the about:config panel.

<Minutes later>
Applying this fix does rectify the problem with the CBC MP3 clip. Unfortunately, other scenarios I encountered with the same problem wasn't eliminated, to my disappointment. One common problem is playing what is presumably mono MP3 clips on Amazon music pages, such as on CD album product listings. In this case, regardless of the boolean setting of this new parameter, the same type of extreme distortion still occurs under Win-XP with SM 2.46. Take the track samples at this URL below for instance. The distortion is extreme and renders the audio completely unuseable:

https://www.amazon.com/dp/B0002ZDWIU/

Frank Lion

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Post Posted May 2nd, 2017, 4:32 am

webmoebius wrote:... as I haven't figured out a way to delete manually added parameters in the about:config panel.

Right click unwanted manually added entry and select 'Reset'. On restart, it'll be gone.

webmoebius wrote: One common problem is playing what is presumably mono MP3 clips on Amazon music pages, such as on CD album product listings. In this case, regardless of the boolean setting of this new parameter, the same type of extreme distortion still occurs under Win-XP with SM 2.46. Take the track samples at this URL below for instance. The distortion is extreme and renders the audio completely unuseable:

https://www.amazon.com/dp/B0002ZDWIU/

Those samples aren't going to be in mono. Link plays fine on Linux, I'll check it out next time I'm in XP. But, I'll tell you now, on XP they will play fine, as I've played music clips on Amazon before and would have noticed if they were wrong.

Disable any existing plugins before retesting, as this is not a SM 2.46 or XP problem. Either way, we'll get to the bottom of it. :)
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webmoebius
 
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Joined: January 21st, 2007, 12:52 pm

Post Posted May 2nd, 2017, 5:10 am

Frank Lion wrote:Those samples aren't going to be in mono. Link plays fine on Linux, I'll check it out next time I'm in XP. But, I'll tell you now, on XP they will play fine, as I've played music clips on Amazon before and would have noticed if they were wrong. Disable any existing plugins before retesting, as this is not a SM 2.46 or XP problem. Either way, we'll get to the bottom of it. :)


Actually some Amazon samples are in mono (I've come across some before), though this particular Amazon page's samples are in stereo. The distortion is exactly the same type however, and for the longest time up until recent SM versions, I had no such distortion on Amazon or with mono MP3 clips, but your insight might provide some technical enlightenment. I have actually just test played the Amazon page again with SM 2.46 running in safe mode and disabled all add-ons at the safe mode start up option box. The problem remains the same, as I expected.

Frank Lion

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Post Posted May 2nd, 2017, 6:14 am

webmoebius wrote:Actually some Amazon samples are in mono (I've come across some before)

I meant that by default they are not, I know that stuff that was originally recorded in mono, Dean Martin, etc. would be.

Anyway, I'll look into it. Before I forget - SafeMode doesn't disable plugins, that has to be done manually.
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therube

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Post Posted May 2nd, 2017, 8:07 am

Frank Lion wrote:Put about:config in the addressbar and press Enter. Right click any entry in the about:config window and select New > Boolean and put this as the entry - media.forcestereo.enabled and make sure that it is selected as false. This only needs doing once.

Refresh your audio page and your problem will be gone...as if by magic.

Works, like you said, as if by magic :-).


Seems this was the Bug 1305826 mono mp3 plays garbled with pops and distorting...



webmoebius wrote:The distortion is extreme and renders the audio completely unuseable:
https://www.amazon.com/dp/B0002ZDWIU/

True.
media.forcestereo.enabled does not help.
Downloaded, played in MPlayer, the clip sounds OK.
Code: Select all
General
Complete name                            : C:\64%2F30%2F202887410_S64.mp3
Format                                   : MPEG Audio
File size                                : 242 KiB
Duration                                 : 29s 936ms
Overall bit rate mode                    : Constant
Overall bit rate                         : 64.0 Kbps
Album                                    : Uma Batida Diferente
Album/Performer                          : Bossacucanova
Part/Position                            : 1
Part/Total                               : 1
Track name                               : Bom Dia Rio (Posto 6)
Track name/Position                      : 1
Track name/Total                         : 11
Performer                                : Bossacucanova
Genre                                    : International
Recorded date                            : 2007
Writing library                          : LAME3.97
Copyright                                : (C) 2004 Ziriguiboom/Crammed Discs
Cover                                    : Yes
Cover type                               : Cover (front)
Cover MIME                               : image/jpeg
Comment                                  : Amazon.com Song ID: 202887410

Audio
Format                                   : MPEG Audio
Format version                           : Version 2
Format profile                           : Layer 3
Mode                                     : Joint stereo
Mode extension                           : MS Stereo
Duration                                 : 30s 66ms
Bit rate mode                            : Constant
Bit rate                                 : 64.0 Kbps
Channel(s)                               : 2 channels
Sampling rate                            : 22.05 KHz
Compression mode                         : Lossy
Stream size                              : 234 KiB (97%)
Writing library                          : LAME3.97
Encoding settings                        : -m j -V 4 -q 3 -lowpass 11 -b 64

(Note that mediainfo isn't always accurate in what it reports.)
Mozilla/5.0 (Windows; U; Windows NT 6.1; en-US; rv:1.9.1.19) Gecko/20110420 SeaMonkey/2.0.14 Pinball CopyURL+ FetchTextURL FlashGot NoScript

webmoebius
 
Posts: 205
Joined: January 21st, 2007, 12:52 pm

Post Posted May 2nd, 2017, 3:00 pm

therube wrote:True. media.forcestereo.enabled does not help. Downloaded, played in MPlayer, the clip sounds OK.


Thanks for confirming that this stereo MP3 clip generates the same severe distortion problem. Based on the type of distortion I hear, I fear that it is most likely due to the same cause by an internal SM audio codec. But we'll see what emerges. My audio plug ins have not really changed, but this problem arose relatively recently when I updated to newer versions of SM. I also applied the new configuration parameter to another Win-XP user's system that had SM 2.46 installed and a subsequent test found that the mono MP3 clip distortion was resolved while the Amazon clips continue to play with the same extreme distortion.

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