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Results of trascoding test to 128k
shadowking
post Aug 1 2004, 08:57
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I finished a short but interesting test today. My aim was to test the effects of high bitrate lossy transcoding using conventional codecs like lame mp3 and also to test the hybrid codecs such as wavpack.

Task is simple: transcode a large lossy file into a 128k mp3 so it will be suitable for portable players. I chose lame 3.96.1 APS, wavpack lossy around 400k and freeformat mp3 at 384k. I chose freeformat to test its reliability considering the popularity of allofmp3.com. These files were transcoded into 128k mp3 cbr using lame 3.96.1 - reference is 128k mp3. 128k is still popular with the masses and makes it easier to perform tests like these. The sample I chose was the wicked 'amnesia' .

This test was done casualy in a normal enviroment.

Now some results:

1) Mp3 128k transc from Freeformat 384k vs. original 128k mp3

ile A: file://H:\temp\abx tests\amnesia128cbr.mp3
File B: file://H:\temp\abx tests\amnesia cbr128 ff384.mp3

15:56:04 : Test started.
15:57:18 : 01/01 50.0%
15:58:10 : 01/02 75.0%
15:58:58 : 01/03 87.5%
15:59:58 : 01/04 93.8%
16:00:55 : 02/05 81.3%
16:00:59 : Trial reset.
16:03:01 : 01/01 50.0%
16:04:07 : 02/02 25.0%
16:04:19 : 03/03 12.5%
16:04:32 : 03/04 31.3%
16:04:58 : 04/05 18.8%
16:05:04 : 04/06 34.4%
16:05:13 : 04/07 50.0%
16:05:22 : 05/08 36.3%
16:05:27 : 06/09 25.4%
16:05:32 : 06/10 37.7%
16:06:47 : Trial reset.
16:06:54 : 01/01 50.0%
16:07:04 : 02/02 25.0%
16:07:14 : 03/03 12.5%
16:07:20 : 04/04 6.3%
16:07:29 : 05/05 3.1%
16:07:46 : 05/06 10.9%
16:07:51 : 05/07 22.7%
16:08:00 : 05/08 36.3%
16:08:06 : 05/09 50.0%
16:08:11 : 05/10 62.3%
16:09:32 : 06/11 50.0%
16:09:38 : Trial reset.
16:09:43 : 01/01 50.0%
16:09:47 : 02/02 25.0%
16:09:52 : 03/03 12.5%
16:10:01 : 04/04 6.3%
16:10:11 : 05/05 3.1%
16:10:31 : 06/06 1.6%
16:10:39 : 07/07 0.8%
16:10:43 : 08/08 0.4%
16:10:48 : 09/09 0.2%
16:10:52 : 10/10 0.1%
16:10:57 : 11/11 0.0%
16:11:01 : 12/12 0.0%
16:11:34 : 13/13 0.0%
16:11:39 : 14/14 0.0%
16:11:43 : 15/15 0.0%
16:11:47 : 16/16 0.0%
16:11:51 : Test finished.

----------
Total: 30/42 (0.4%)


1.7-3.8 secs is were I found bad noises and dropouts. (16/16)


2) 128k mp3 transc from Lame APS 3.96.1 vs. original 128k mp3

File A: file://H:\temp\abx tests\amnesia128cbr.mp3
File B: file://H:\temp\abx tests\amnesia 128 transc aps .mp3

17:01:15 : Test started.
17:02:08 : 01/01 50.0%
17:02:16 : 02/02 25.0%
17:02:22 : 03/03 12.5%
17:02:29 : 04/04 6.3%
17:02:49 : 04/05 18.8%
17:02:56 : 05/06 10.9%
17:03:05 : 06/07 6.3%
17:03:52 : 07/08 3.5%
17:03:59 : 08/09 2.0%
17:04:05 : 09/10 1.1%
17:04:16 : 10/11 0.6%
17:04:41 : Test finished.

----------
Total: 10/11 (0.6%)


1.7-3.8 secs: Better than freeformat ! ?? but new ringing / smearing. Overall much less noisy than freeformat.

Another trial with same files (1st 3 secs):

File A: file://H:\temp\abx tests\amnesia128cbr.mp3
File B: file://H:\temp\abx tests\amnesia 128 transc aps .mp3

16:24:09 : Test started.
16:26:47 : 01/01 50.0%
16:26:55 : 01/02 75.0%
16:27:10 : Trial reset.
16:27:30 : 01/01 50.0%
16:27:38 : 02/02 25.0%
16:27:51 : 03/03 12.5%
16:28:03 : 04/04 6.3%
16:28:11 : 04/05 18.8%
16:28:43 : 05/06 10.9%
16:29:11 : 06/07 6.3%
16:29:57 : 07/08 3.5%
16:30:05 : 08/09 2.0%
16:30:51 : 09/10 1.1%
16:31:13 : 10/11 0.6%
16:31:47 : 10/12 1.9%
16:31:57 : 11/13 1.1%
16:32:05 : 12/14 0.6%
16:32:18 : Test finished.

----------
Total: 13/16 (1.1%)

Fist 2 secs HF ringing


3) mp3 128k transc from wavpack 400k vs. original 128k mp3:

File A: file://H:\temp\abx tests\amnesia128cbr.mp3
File B: file://H:\temp\abx tests\amnesia128 transc wv400.mp3

16:40:03 : Test started.
16:40:33 : 00/01 100.0%
16:40:54 : 01/02 75.0%
16:40:58 : 01/03 87.5%
16:41:05 : 02/04 68.8%
16:41:09 : 03/05 50.0%
16:41:14 : 03/06 65.6%
16:41:20 : 04/07 50.0%
16:41:24 : 05/08 36.3%
16:41:29 : 06/09 25.4%
16:41:33 : 06/10 37.7%
16:41:44 : 06/11 50.0%
16:41:51 : 06/12 61.3%
16:41:56 : Test finished.

----------
Total: 6/12 (61.3%)


The 1.7-3.8 secs are transparent to me.

Another trial - 1st few secs:

File A: file://H:\temp\abx tests\amnesia128cbr.mp3
File B: file://H:\temp\abx tests\amnesia128 transc wv400.mp3

16:34:17 : Test started.
16:34:24 : 01/01 50.0%
16:34:28 : 02/02 25.0%
16:34:35 : 02/03 50.0%
16:34:41 : 02/04 68.8%
16:34:45 : 03/05 50.0%
16:34:52 : 03/06 65.6%
16:35:12 : 04/07 50.0%
16:35:21 : 04/08 63.7%
16:35:32 : 04/09 74.6%
16:36:02 : 05/10 62.3%
16:36:19 : 05/11 72.6%
16:36:29 : 06/12 61.3%
16:36:34 : 07/13 50.0%
16:36:38 : 07/14 60.5%
16:36:45 : 08/15 50.0%
16:36:49 : 09/16 40.2%
16:36:55 : 10/17 31.5%
16:37:02 : 11/18 24.0%
16:37:14 : 11/19 32.4%
16:37:25 : 11/20 41.2%
16:37:27 : Test finished.

----------
Total: 11/20 (41.2%)

1st secs cannot abx hf boost / ringing.


Conclusion: Amnesia is a tough sample. transcoding from APS introduces hf ringing distortions. Freeformat was a big disappointment as there was less ringing but much worse noise than APS !.

Transcoding from high bitrate mp3 to 128k is questionable and with this sample its bad news.

Wavpack showed no audiable loss to me here. I am going to do more tests soon, but for now I can say that hybrid lossy around 400k or maybe lower can be used for general archiving and transcoding when space is short or you just don't like 870k lossless files. I am not advocating it as a replacement for true lossless though but with the correction files you might get the best of both.


--------------------
Wavpack -b450s0.7
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Digisurfer
post Sep 3 2004, 23:12
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From: Canada
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QUOTE (shadowking @ Aug 1 2004, 01:57 AM)
I chose freeformat to test its reliability considering the popularity of allofmp3.com.
*

Good work here. By the way, I've seen freeformat 384 kbps mentioned before in regards to allofmp3, including in a popular review out there. I signed up just for the heck of it to see what all the fuss was about (after it was mentioned on The Screensavers), and noticed that when you order sutff using their Online Encoding feature, it will tell you the source format of the file you're about to encode. 99% of the time it says -alt-preset standart (the t is a typo obviously). If true that would mean very little of their music is actually in 384 kbps freeformat. Bad news for transcoding. Makes me wonder how much of their lossless stuff can be trusted as well. The problem is you just don't know where the source came from. Plus you have no control over the ripping process (are all their songs listend to for errors?). In the end I decided I didn't really care for the service, despite it being so cheap (and yes, I know allofmp3 is a grey area legally speaking). I'd much rather be able to buy songs from a reputable store in a lossless format. Anyways, thanks for the tests. Interesting stuff.
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