MP3 sounds distortion

[Nerfboy]

I just started editing in Edius 4.6 (HDV project).

I have added a song in mp3 format that sounds fine from it's source file, but when I add it to the timeline the beginning is a bit distorted, but then clears up.

Anyone have an idea about this one?

[Nerfboy]

Hmm, converted to Wav and sounds fine, just don't know why that would happen.

[antonsvideo]

most mp3 files especially variable bitrate ones I tried are bad quality and cause artefacts in a 48k project

so I convert the 44.1k mp3's to wav 48k using the Easy CD Extractor File cnverter from poikosoft.com

it allows you to copy an entire music CD to hard disk and 48k wav in 5 minutes

remember, video is 48k, CD audio is 44.1 and most mp3 are 44.1 or less

[skier-hughes]

MP3 is a video file, but with the video removed, so you end up with an audio file which often has corrupted headers and leads to editing problems.
Stick to using wav and you'll be fine.

[Nobby Tucker]

Always stick to 48K or you may get drift over the timeline!

[STORMDAVE]

MP3 is a video file, but with the video removed, so you end up with an audio file which often has corrupted headers and leads to editing problems.
Stick to using wav and you'll be fine.

MP3 is a lossy audio format, not a video format

[GrassValley_KH]

Correct.

We're (Thomson) part of the original engineering of MPEG-1 Audio Layer 3 and practically own the license for it. :)

[skier-hughes]

My bad understanding of previously read material.

Though reading through links from Stormdaves link I came across this little snippet....

Sisvel S.p.A. and its U.S. subsidiary Audio MPEG, Inc. previously sued Thomson for patent infringement on MP3 technology

Ooops.

Why is MP3 such a blighter to edit then? Is it jsut the vast array of encoders and not suitable decoders at the other end?

[GrassValley_KH]

MP3 is compressed audio, like MPEG-2 is compressed video..

While to a user, the decoding might seem trivial on a computation level, the work still has to be done. At the same time as decoding video and then hoping it all goes out in sync.

[UlfLaursen]

I always convert to wav, and with todays fast internet / ftp's etc. it's easier to move moderate wav files arround.

/Ulf

[GrassValley_BH]

The root issue is simply this...

Editing involves a successive number of video or audio frames.
Playback is instead the decoding of a continual stream.


While at first glance they appear to be the same, you can think of it this way...

If you're walking a path from point A to point B, taking pictures.

In editing, you're quickly instructing the person to get from their exact location to a specific point on the path, then to take a pciture. The person's location is absolute as it involves a known start point followed by relative movement.

In playback, the person is on the path and you're just instructing them where to go relative from where they currently are and take a picture. We don't know or care exactly where the person is, just where they are relative to the next point.


There's a subtle, but important difference. In both cases the person has pictures from point A to point B, but in the case where each picture can be taken individually, the person is always at a known position.

In the case of intra-frame vs inter-frame encoded data, when using inter-frame encoded data (i.e. MPEG-2 Long-GOP), in editing there's some amount of work that must be done to "figure out where you are" before you can give the instructions to get to the correct point on the path.