mystery Avi - Scratchy sound on original avi but good sound on edited wmv

[Calle001]

Mystery .avi file
I have an old .avi file where the sound is just scratchy, no mystery there but I have a wmv file presumably derived from the .avi file but the wmv HAS the sound. Has anyone any ideas what may have happened and how to fix it?

Quick background:
In 2006 we recorded a birthday party with my girlfriends computer, it was running XP and recording was done with a Logitech Quickcam for notebooks probably using quickcapture (quickcam 8.4.8). My girlfriend then edited parts of the clips in Windows Movie Maker, converting it to a .wmv and sent it to our friends. However, in the original clips a friend of mine held a hilarious monolog and subsequently fell off the chair. I really want this clip for a thing we are doing for his stag-party.

NOW, The how can the original avi clip have weird scratchy sound, just static really, and the edited version, a wmv clip, have perfect sound?

I ran them through mediainfo and got the data attached below.

I have tried the following without success:
- Recoding the avi to different format.
- Using audacity to check the sound profile, and the avi has a sound profile that looks like solid band of static with a few spikes. I have tried every filter on audacity with out result
- Firing up the old computer and checking if the sound is there – it is not but the original has been copied to different folders since it’s creation.
- I tried to replicate the situation with the cam, first recording then running through moviemaker but those clips retain the sound.

If the file is simply corrupt it must have happened when my girlfriend moved it to another folder in the same computer and it must have happened with all the avi files from the Logitech cam (they all have the same problem). Is this likely?

Could the Logitech software have used some weird codec or mux that subsequently disappeared in later updates so that the current software uses the wrong demux or codec to open the avi?

Could the program have written the wrong demux /codec info into avi? Is there a player where I can force the use of a specific codec to test this.

Could it be some sort of little-endian – Big-endian issue?

Please someone help me with this!


Complete name Video 3.avi (without sound) last change: 2006-08-20 16:46

Format : AVI
Format/Info : Audio Video Interleave
File size : 145 MiB
Duration : 7 min 55 s
Overall bit rate : 2 556 kb/s
IsTruncated : Yes

Video
ID : 0
Format : Indeo 4
Codec ID : IV50
Codec ID/Info : Intel Indeo Video 5.0 Wavelet
Duration : 7 min 55 s
Bit rate : 2 378 kb/s
Width : 640 pixels
Height : 480 pixels
Display aspect ratio : 4:3
Frame rate : 15.000 FPS
Bits/(Pixel*Frame) : 0.516
Stream size : 135 MiB (93%)
Title : qc2.avi Video #1

Audio
ID : 1
Format : PCM
Format settings, Endianness : Little
Format settings, Sign : Unsigned
Codec ID : 1
Duration : 7 min 55 s
Bit rate mode : Constant
Bit rate : 176.4 kb/s
Channel(s) : 1 channel
Sampling rate : 22.05 kHz
Bit depth : 8 bits
Stream size : 10.0 MiB (7%)
Alignment : Aligned on interleaves
Interleave, duration : 2954 ms (44.32 video frames)
Title : qc2.avi Audio #1

 
Complete name Party 2006.wmv (With sound) last change:2006-08-20 17:43
Format : Windows Media
File size : 26.4 MiB
Duration : 4 min 13 s
Overall bit rate mode : Constant
Overall bit rate : 873 kb/s
Maximum Overall bit rate : 874 kb/s
Encoded date : UTC 2006-08-20 16:40:48.328
Application : Windows Movie Maker 2.1.4026.0

Video
ID : 2
Format : VC-1
Format profile : MP@ML
Codec ID : WMV3
Codec ID/Info : Windows Media Video 9
Codec ID/Hint : WMV3
Description of the codec : Windows Media Video 9
Duration : 4 min 13 s
Bit rate mode : Constant
Bit rate : 768 kb/s
Width : 640 pixels
Height : 480 pixels
Display aspect ratio : 4:3
Frame rate : 25.000 FPS
Color space : YUV
Chroma subsampling : 4:2:0
Bit depth : 8 bits
Scan type : Progressive
Compression mode : Lossy
Bits/(Pixel*Frame) : 0.100
Stream size : 23.2 MiB (88%)
Language : Swedish

Audio
ID : 1
Format : WMA
Format version : Version 2
Codec ID : 161
Codec ID/Info : Windows Media Audio
Description of the codec : Windows Media Audio 9.1 - 96 kbps, 44 kHz, stereo (A/V) 1-pass CBR
Duration : 4 min 13 s
Bit rate mode : Constant
Bit rate : 96.0 kb/s
Channel(s) : 2 channels
Sampling rate : 44.1 kHz

[LigH.de]

Channel(s)                               : 1 channel 
Sampling rate                            : 22.05 kHz 
Bit depth                                : 8 bits

8 bit audio ... that will be the main reason for low quality to begin with. But depending on the settings during the conversion to WMA, including upsampling to 44.1 kHz, the result may have been filtered mostly in the higher frequencies, so that the annoying artefacts will have been a bit damped, in comparison to playing this original audio directly. Possibly even avoided some clipping in extreme volumes.

[Calle001]

Channel(s)                               : 1 channel 
Sampling rate                            : 22.05 kHz 
Bit depth                                : 8 bits

8 bit audio ... that will be the main reason for low quality to begin with. But depending on the settings during the conversion to WMA, including upsampling to 44.1 kHz, the result may have been filtered mostly in the higher frequencies, so that the annoying artefacts will have been a bit damped, in comparison to playing this original audio directly. Possibly even avoided some clipping in extreme volumes.

Yes, that is the idea have gotten from others but the more I work with the audio it seems that this it may be a codec problem.
I tried to replicate the conversion to WMA but I get a perfect sample of the same scratchy noise as in the original.
Either the all the AVI originals have become corrupted, which I find a little bit unlikely, or the files are encoded with some weird codec no longer used and wrongly called pcm u8.

Still no idea and all hints are welcome.

This is picture of the waveform in audacity. The grey box in the middle is an attempt at declipping. In the very left is a closeup of the audio. With further zoom on the timeline below

[jagabo]

The audio is definitely not being decoded correctly. Can you upload a short sample of the original audio?

[Cornucopia]

Little-endian being decoded as big-endian (or vice-versa)?

Scott

[jagabo]

There is no little endian vs. big endian with 8 bit values. But it might be signed (-128 to +127) vs. unsigned (0 to 255). "pcm u8" implies unsigned 8 bit pcm.

[Calle001]

Yes, used ffplay -i c:\ffmpeg\video3.avi -acodec [xxxx] to force the player to use a specific codec but got more or less the same scratchy result in all attempts, at least with various versions of pcm.
If the codec was not compatible att all there was no sound.
Of course I am a beginner with ffmpeg/ffplay so I may have written the command wrong.

[Calle001]

I used ffmpeg -i video3.avi acodec copy ...etc to get this audio file out

[Calle001]

I am starting to lean towards corrupt files though.
I have tried every angle on codecs and every filter on the audio, still nothing that even resembles sound.
Old computer, long unused - I guess you get weird effects after some time.

[jagabo]

There's nothing wrong with the audio in that WAV file. It's simply silent with a little noise. The samples are bouncing back and forth between 126, 127, and 128 (8 bit unsigned integers with possible values from 0 to 255). They look the way they do in the Audacity screen caps you posted because you applied a large amplification.

Open the original video file in a hex editor and look for the audio chunks. If the WAV file accurately reflect the original audio you'll see audio chunks like:



Note:

7e = 126
7f = 127
80 = 128

So the above represents a flat waveform (silence) with a little noise, exactly what you hear when you play the file.

[JVRaines]

I am starting to lean towards corrupt files though.

The file is not corrupt. It's a perfectly valid audio stream that happens to have some minor noise for a program. What are the creation and last change timestamps on your files?

[Calle001]

Yes, unless I have managed to screw up the audio extraction this is likely the case.
Having ruled out everything else the least improbable is likely to the truth. The avi files are not the original ones, though why there is no sound I have no idea.

Oh well, I guess this is one of life's little mysteries.

Thanks everyone for taking time to answer and comment on this.