Introduction

These 2 parts are just here to give you some clues about how to detect DVD VCD sourced and bootlegs mp3 sourced. I'm not a sound engineer, so i don't pretend to be totally right about what is following. I'm just arguing with the "bad" experiences i had in some trades with bootlegs i'm sure are mp3 sourced and DVDs i'm sure are VCD sourced, and i try to share with you my experience about these shitty conversions...

Part 1 : VCD detection guide

After having received some DVD VCD sourced, i do prefer informing people how to dectect this shitty DVD.

I really donít see the point of having VCD on DVD..... The meaning of DVD is to have to best enabled quality .... with no loss of quality between the original source and the final result on DVD... But VCD are by definition lossy quality because real bad compression is used, the same way mp3 is a bad compression of original audio cd.....

There are 2 easy ways to dectect DVD VCD sourced :

1) The size of the DVD VCD sourced are about 1.2 Go to 1.5 Go (while real DVD size is about 3.5 Go to 4.5 Go)

2) If you read the DVD VCD sourced with PowerDVD, the video format is shown (MPEG-2 for real DVD and MPEG-1 for VCD sourced.)

Anyway, that's true that a S-VCD has a MPEG-2 encoding.... So this is a little comparaison between VCD / S-VCD and DVD format :

Video File Comparison
Format
VCD
SVCD
 
DVD
HDDVD
HDTV
(WMVHD)
DivX
XviD
WMV
MOV
Quick-
Time
RM
Real-
Media
DV
Resolution
NTSC/PAL
352x240
352x288
480x480
480x576
 
720x480≤
720x576≤
1440x1080≤
1280x720≤
640x480≤ 640x480≤ 320x240≤ 720x480
720x576
Video
Compression
MPEG1
MPEG2
MPEG2, MPEG1
MPEG2
(WMV-
MPEG4)
MPEG4
Sorenson, Cinepak, MPEG4
RM
DV
Video bitrate
1150kbps
~2000kbps
~5000kbps
~20Mbps
(~8Mbps)
~1000kbps
~1000kbps
~350kbps
25Mbps
Audio
Compression
MP1
MP1
MP1, MP2, AC3, DTS, PCM MP1, MP2, AC3, DTS, PCM MP3, WMA, OGG, AAC, AC3 Sorenson, Cinepak, MP3 RM DV
Audio bitrate
224kbps
~224kbps
~448kbps
~448kbps
~128kbps
~128kbps
~64kbps
~1500kbps
Size/min
10MB/min
10-20MB/min
30-70MB/min ~150MB/min
(~60MB/min)
 
4-10MB/min 4-20MB/min 2-5MB/min 216MB/min
Min/74min CD
74min
35-60min
10-20min ~4min
(~10min)
60-180min 30-180min 120-300min 3min
Hours/DVD
N/A
N/A
1-2hrs
(2-5hrs™)
~30min
(~1hrs)
7-18hrs 3-18hrs 14-35hrs 20min
Hours/
DualLayerDVD
N/A
N/A
2-4hrs
(5-9hrs™)
~55min
(~2hrs)
13-30hrs 6-30hrs 25-65hrs 37min
Computer CPU Usage
Low High Very High Super high Very High High Low High

But you still have a doubt because your DVD has the good format (DVD standards), well ...., only your eyes can make the real difference !!!

 

Part 2: MP3 detection guide

 

I find these informations on a very good page. You can check at http://members.optushome.com.au/mattboland/mp3bug.htm

When a wave file is encoded to MP3, the higher frequencies are discarded to achieve a file size up to ~1/10th the size of the original. This smaller file size results in less time downloading. The different bit rates refer to the amount of data required per second. That is, 96 kilobits per second for a 61 second song is 5856000 bits, which is equal to 732000 bytes.

Now, there are many many different encoders out there, each claiming to 'sound' better, or encode quicker etc. Using a poor DAC, using a sound card that resamples, analog transfers et al can all effect the 'sound' of an audio file. This page will be used to compare the visual representation of these audio files.

The following graphs are pretty self explanatory. I've used the same song as my test file. It was encoded to 96kbps, 128kbps, 160kbps, 192kbps, 256kbps and 320kbps constant bit-rate mp3 files. Variable bit-rate mp3 files were also created at 10, 50 and 100 values (where 10 is the lowest quality setting and 100 is the highest). These were created using MP3/mp3Pro fraunhofer IIs encoder via CoolEdit Pro 2.
I also transferred the song to mini disc and recorded at SP and LP2 modes using a Sharp MD-MT99W with ATRAC 3 compression.

The following graphs are the visual representations of the resulting audio files.

96kbps     0.732MB


Notice sharp decline after 11KHz and not much after that

 

128kbps     0.976MB


Notice sharp decline after 16KHz and not much after that

 

160kbps     1.22MB


Notice sharp decline after 16KHz and not much after that

 

192kbps     1.464MB


Notice sharp decline after 16KHz and not much after that

 

256kbps     1.952MB


Notice sharp decline after 16KHz and not much after that

 

320kbps     2.440 MB


Notice sharp decline after 16KHz and not much after that

 

VBR10     0.724MB


Notice sharp decline after 13.5KHz and not much after that

 

VBR50     1.003MB


Notice sharp decline after 15KHz and not much after that

 

VBR100     1.676MB


Notice sharp decline after 16KHz and not much after that

 

MD


Notice sharpish decline after 16KHz yet not full cutoff

 

MDLP2


Notice bluntish decline after 15KHz yet not full cutoff as well as lower db from 20-15000Hz

 

Uncompressed wave file     10.750MB

 

File
Frequency cut-off
Data after cutoff
96kbps
11000Hz
< -108dB
128kbps
16000Hz
< -108dB
160kbps
16000Hz
< -108dB
192kbps
16000Hz
< -108dB
256kbps
16000Hz
< -108dB
320kbps
16000Hz
< -108dB
VBR10
13500Hz
< -108dB
VBR50
15000Hz
< -108dB
VBR100
16000Hz
< -108dB
MD
16000Hz
~ -96dB
MDLP2
15000Hz
< -96dB       > -108dB
Uncompressed
none
> -84dB

Observing the frequency analysis of a song whilst playing, even an mp3, the values after the 'cutoff' may fluctuate, however these values are not a true representation of the file. In these images, I have chosen a specific point in the song where I can best determine the true file properties.

 

 

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