INTERACT FORUM

Please login or register.

Login with username, password and session length
Advanced search  
Pages: [1]   Go Down

Author Topic: Strange Problem with MP3 "fast" encoding: loud noises  (Read 6069 times)

dvdr

  • Recent member
  • *
  • Posts: 29
Strange Problem with MP3 "fast" encoding: loud noises
« on: September 03, 2008, 01:48:33 am »

Hi

the problem in a nutshell: encoding with the "fast" MP3-VBR-option caused loud noises in the mp3-files.

Full description:
I am running the latest MC 11 version, and yesterday, I updated the music-collection on my Ipod Nano (2nd Gen.) with new music.
As encoding settings, I chose MP3, High Quality (VBR) , "fast encoding", 4 concurrent encoding sessions, using the MC11 presets and not a commandline switch.
Since I have a double-core 4Ghz processor with 2 GB of RAM, I thought, 4 parallel encoding processes should not be too much - encoding speed seemed nice and fast on all 4 processes.
Original files are flac-files, residing on a file-server and were accessed over ethernet, I did not have the impression, that this caused any problem.
Encoding and filling the Ipod with about 600 files took about 1:40 hrs.
Listening to the files, I heard short loud noises, especially after the first 7 - 10 seconds, but also later during the songs. These noises turned out to be other short parts of the song being "thrown" in on another location of the song.
I am sure, that this problem does not relate to the "Lame high VBR skipping problem" described in this forum, since the problem also occured, when I locally played back the files on my computer (either from the Ipod or copying them over to the computer's harddisc beforhand). So, I guess, it is a problem with the simultaneous conversion from flac->mp3 and/or has to do something with the parallel encoding processes and/or the "fast" option.
A quick test, just using ONE encoding process at a time and disabling the "fast" option did not produce any problemsc (so it is definitely NOT the VBR-problem with the Ipod Nano, as you sure will agree, otherwise, playing back that "normal high"-quality VBR from the Ipod would have produced skips or drop-outs as well).

So, here's the questions:

1.) Is the problem caused by the "fast" option alone
2.) Could the problem be related to the 4 concurrent encoding processes on a 4 GHz double-core Pentium?
3.) Could the problem be related to the need to both decode from flac and encode to MP3
4.) Could the problem be related to Network problems - would a normal Ethernet be too slow for that?
5.) Could the problem be related to the Lame.dll this version of MC11 uses, can I update it manually somehow, if needed?
6.) Should I use the commandline option with another Lame.exe, and where would I put this exe, so MC11 would find it?

I would love to keep any options, that make the encoding-process as fast as possible, since with the same amount of music and the encoder set to single encoding and "normal" speed, after 6 hours, the encoding still is not done...

Thanks for any help!
Logged

Alex B

  • MC Beta Team
  • Citizen of the Universe
  • *****
  • Posts: 10121
  • The Cosmic Bird
Re: Strange Problem with MP3 "fast" encoding: loud noises
« Reply #1 on: September 16, 2008, 01:03:13 pm »

Since no one else has answered I'll try.

I think the answer to all your questions is no.  It should not be possible to use a "too fast" LAME setting. The LAME encoder works always as fast as it can. It processes incoming the PCM data when it is entered, bit by bit. Unlike audio playback or CD burning the encoding process does not need a steady stream. The encoding speed can be slower than 1x if needed. (This could actually happen in the early days of MP3 when the PCs were much slower.)

Similarly the decoding process should not be depended on the available resources or LAN bandwidth. It should just run slower if the LAN gets momentarily congested. (Which can happen when you are running four decoders.)

I'd say that something else is going on, but I have no idea what it could be.

Maybe MC11 has a bug or you have a hardware problem. I wonder if a RAM problem that occurs only when the system is extremely stressed can cause what you explained: "These noises turned out to be other short parts of the song being "thrown" in on another location of the song."

As a test, you could try what happens when the files are encoded to a local HD folder instead of syncing the iPod.
Logged
The Cosmic Bird - a triple merger of galaxies: http://eso.org/public/news/eso0755
Pages: [1]   Go Up