Slow conversion

[menotune]

I am having a problem batch converting flac->mp3. Conversion seems to start out fine (4-5x RTE), but gradually gets slower and slower. After running for about 15 minutes, the speed approches 1x RTE, and remains there.

I have PP installed (within 30 day trial period - v11).
I am running on 2Gz Pentium / Win XP.
No other processes are running, no DSp used, professional freq conv is DISabled, priority='below normal'.

Other conversion programs (which do create a temp wav file) generally run at 4-5x RT on the same machine.

1x RT is too slow for my needs. What is going on here? Anyone else seen this?

[LtData]

Re: Slow conversion

When you say batch converting, I assume you mean there is one instance of dMC running. Now, as to why it's slowing down, it might be related to your HDD not being able to tranfer the data fast enough for the CPU to process it, mabye? What are your system specs?

[menotune]

Re: Slow conversion

By batch processing, I mean several directories of flacs choosen by 'dMC File Selector'.

System Specs: 2 GHz Pentium, 512M RAM, WinDoze XP on a Toshiba Satellite Laptop. The disk activity light blinks at a slow rate (disk not overloaded). Task Manager shows 'MusicConverter.exe' using 90%+ of the CPU.

It's not the hardware. As mentioned, I have no problem doing this with other software ... for example: a batch file which uses flac.exe to convert flac to wav, then lame.exe to convert to .wav to MP3. In both cases, I am using alt-preset-extreme for MP3 encoding.

The batch file will convert the flacs in just over an hour. DBpowerAmp converter is taking about 6-7 hours. I would just use the batch file, but it currently won't transfer id tags. It is this feature which attracted me to the dBpowerAMP converter.

[LtData]

Re: Slow conversion

When you are converting, are you leaving the computer idle or are you doing other tasks? Are you running multiple things in the background or just letting it convert? Does the screensaver kick on or any other powersave function kick in?

[menotune]

Re: Slow conversion

As mentioned in the original post:

No other processes are running...

The speed issue happens well before my screen blanks. No screensaver installed - just blanking.
Really, it is nothing that obvious.
If I have time, I will try other audio formats to see if it could be specific to flacs, etc.

Thanks for the quick responses!

[LtData]

Re: Slow conversion

I'd try other formats to see if it's just FLAC or a general dMC problem. Although, I will say the conversion speed does drop a little over the period which your converting, but shouldn't be going from 4-5x to 1x. Mabye down to like 3x, but not 1x.

[petriburg]

Re: Slow conversion

In your post 12-25-04, you say that you are using the setting alt/preset/extreme. I don't recall this setting being recommended previously by anyone - normally, most recommendations are for using alt/preset/standard. I would suggest giving this a try - it may not solve your problem, but I don't think there is much to be gained by using any other - it's the setting I invariably use for my conversions.

[menotune]

Re: Slow conversion

Thank you.

AP-Extreme provides a slightly higher average bitrate, which I find appropriate for classical music archiving. I have been using this method for a while.

I haven't done any testing as far as encoding speed comparisions between the two methods, but in theory, there shouldn't be too much difference - other than disk output (A.P.Extreme = bigger files).

As a side note, I have tried a few other conversions, with the same speed problems. Conversions always start out fast, but gradually get slower and slower. So far, I have tried flac to wav, wav to mp3, wav to flac. I am suspecting something odd about my system here - no idea what though.

Other than my speed issue, I find the dBpwerAMP suite to be an excellent bargain at $14, and I have registered my copy.

[Spoon]

Re: Slow conversion

Try converting to Test Conversion, does the Speed stay constant?

[menotune]

Re: Slow conversion

I performed the following test:

I made 11 copies of the same flac file (93 Mb each) in a test directory, and converted all of them (one instance of dmc) to "test conversion (no write)".
Results:

Conversion started at approx 100X RTE, and dropped gradually to 44x at about the half-way point. The second half (5 files) stayed at a constant 44x. The entire 'conversion' took about 5 minutes.

I thought that disk caching may be an issue, so I rebooted and ran the test again, but the results were identical.

How is the speed calculated? Is it a 'snapshot', an average of the current file, or a moving average of the entire job?

[LtData]

Re: Slow conversion

Wait.. it took you 5 minutes for a test convert? That's not right. A Test Conversion should be quickly, not take 5 minutes. Something's not right somewhere, but I don't know where.

[menotune]

Re: Slow conversion

A GIGAbyte worth of flac - seems reasonable to me. I would assume that the flac 'codec' was executed to convert to wav format (just not written to disk).

[menotune]

Re: Slow conversion

More test results, using the same test data set of 11 flacs (total 1 GB) ...

Using dMC to convert to .WAV: approx 11 minutes
Using batch file calling flac.exe: approx 12 minutes

So, dMC outperformed flac.exe in converting flac to wav (I suppose the dll is quicker than the exe for some reason).

So, it would seem now that my problem is in the creation of the MP3s. I will continue testing in this area. Perhaps it is just that the reporting of speeds is not accurate at the start of conversion.

SPOON: Can you give some insight as to how dMC reports conversion speed (x RTE)?

[Spoon]

Re: Slow conversion

RTE is length of file and time written, so if convert a 60 second file in 6 seconds that is 10x encoding.