DivX
DRF Analyzer - 0.9.5 |
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| DivX DRF Analyzer 0.9.5 opens DivX;)
3.11, DivX 4, DivX 5
and XVID avi files and analyses its quality.
Plots a graphic with the DRF values/quantizers
of each frame. Also plots a graphic with the size of each frame.
Identifies key and dropped frames. A report is generated with
overall technical/statistical characteristics of the file. |
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| Added a small article about the recommended resolution feature
and how is calculated. Click Here. |
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| [New in 0.9.5.1] |
| Just a quick small fix to support DivX 5.0.5. |
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| [New in 0.9.5] |
| Packeted Avi Frames Support for full account of B-Frames in
DivX5 codec. Very CPU intensive, resulting in slower analysis,
when necessary only. |
| New configuration file. Generated automatically with default
values. |
| Minor changes in the report section. |
| Minor source cleaning. Optimized (hopefully) compilation options. |
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| [New in 0.9.4] |
| Command Line Options: DRFanalyzer.exe [filename.avi] [--output
DRFreport.txt] . It is now possible to open a video file
using RightclickOnFile->OpenWith->ChooseProgram->Other.
When generating a DRFreport.txt the program exits automatically
when finished. |
| DRF export feature should be working properly know. Backward
compatible with previous export versions. |
| Minor optimizations. |
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| [New in 0.9.3] |
| Static MFC compilation. No more dlls required. Larger file size... |
| It is no longer necessary to have any codec installed. |
| Identify the FourCC of the avi file. With the mpeg4 user data,
the encoder codec is now completly identified. |
| Suport for the original MS MPEG4 v2 and v3. |
| Should be a little faster. |
| Reading drf export files may result in missing/strange values
in the Report Section. To be fixed in future releases. |
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| [New in 0.9.2] |
| Implemented a MPEG4 bitstream parser class based on XVID source
code. |
| Support for DIVX3.11, DIVX4.x, DIVX5.x and XVID. |
| Support for I, P, B, S frame types. B frames and DivX5 packeted
bitstream support isn't complete yet. |
| Identification of mpeg4 encoder using internal user data string
when available (XVID and DIVX5). |
| Report section was updated with more information. Frame type
statistics, recommended resolution and other minor changes. |
| Reading export files may result in strange values in the Report
Section. To be fixed in future releases. |
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| [New in 0.9.0] |
| Added DivX4 (version 4.12 only) support. The frame structure
seams to change with different versions of DivX4. For instance,
this program doesn't support files that were encoded with version
4.0 of the DivX Codec. For more information click
here. |
| Fixed a small annoying bug. |
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| [New in 0.8.3] |
| Added the option to correct the DRF statistical information
( not the graphics ) by ignoring the last 15000 frames of the
movie ( ~10 minutes ). |
| Minor changes. |
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| [New in 0.8.2] |
| Minor graphical changes. Some thresholds were tuned in the Report
section |
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| [New in 0.8.1] |
| Minor changes. The frame size graphic was not completely draw. |
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| [New in 0.8] |
| - Generates a report with some facts about the file and a subjective
classification of the video quality. |
| - Verifies the deviation to the average of the DRF values. |
| - Exports the analysis to a file for future use, or to show
to someone else the quality of a file. This can be useful when
trading, the export is about 1MB ( ~33% if Zip Compressed) and
can be easily uploaded/downloaded. |
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| ATTENTION: The screen color depth must be 32bit.
RightClickOnDesktop->Properties->Settings. |
| This Program was tested in Windows2000, XP and 2003RC2 only.
In Win95/98/ME, it may not work properly. The Frame Size graphic
isn't draw in Win98se. |
| Reading from a CD-ROM may be slow. |
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| Download: DivX
DRF Analyzer 0.9.5.1 (static binary). |
| Attention: Unfortunately, version 0.9.5 doesn't
support DivX 5.0.5. Should be fixed in 0.9.5.1. |
| Warning: DivX5 packeted B frames should be
correctly identified now, but analysis is slower in those files. |
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| This program was developed using some code from Nandub to
open the Avi File, wich was based in VirtualDub www.virtualdub.org. |
| The C++ MPEG4 Header Bitstream Parser was based on XVID source
code, www.xvid.org. |
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| Because of NanDub/VirtualDub and XVID distribution license,
here
is the source code of DivX DRF Analyzer 0.9.2 (scr) |
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| Any Question/Suggestion: nfj@mail.pt |
| GuestBook:
Write a message - View
Messages |
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Screen Shots |
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| DRF graphic: |
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Green : DRF value between 2 an 4. |
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Yellow : DRF value between 5 an 8. |
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Red : DRF value above 8. |
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| Frame Size graphic: |
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Blue : Frame Size below average. |
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Orange : Frame Size above average. |
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| When there is no DRF value, the frame was dropped by the Codec
when compressing. |
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Information |
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| DRF
values. When encoding, the mpeg4 codec compresses each image
in order to achieve a certain bitrate. The required level of compression
depends on the desired bitrate, image complexity and level of
motion. For each frame, a decision is made, resulting in the DRF
values. The maximum quality is achieved with a DRF value
of 2 (quantizer 1 is possible in XVID). The worst is
obtained with a DRF of 31. Above DRF 8, I consider it to be very
bad quality. The DRF/quantizer represents the quantity of information
discarded by the encoder reducing the frame size. |
| DivX4, 5 and XVID calls it Quantizers. |
| Dropped frames occur when
the codec doesn't have enough bitrate to encode a frame. Then
it is marked as dropped and no information is included. Black
images may also be discarded. |
| A key frame is a special
image that doesn't depend on the previous or future ones. Is required
for seeking the file, improves the image quality in scene changes
and cleans accumulated errors. |
| These factors are very important
for the quality of a DivX but aren't the only ones. The image
resolution is also very important and any smoother filtering performed
when encoding, like the crispness value. A very Low resolution
( below 512 horizontal ) and crispness below 70% can reduce greatly
the quality of the result. This program doesn't analyze this problem. |
The report (starting at version
0.9.2) suggests a resolution in order to achieve a certain DRF/quantizer
average. The target average is 2.8 and assumes that the file
size changes linearly with it. That is not quite true but, for
higher DRF average it is close. |
| Assuming that S1/S2=q2/q1 when
H1=H2 and W1=W2 is a good approximation, the equations for the
resolution are: H2=sqrt(q2/q1)H1 and W2=sqrt(q2/q1)W1. Please
click here for more information.
This is supposed to be an hint, not an absolute true. |
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| A good TWO (2) CD DivX
has an average DRF below 3 (three), no dropped frames and a maximum
DRF of 6 (six) ( 2% max. ).The deviation should be less than 1.
The resolution should be equal or bigger than 608 horizontal.
( DVD 16:9 source ), unless there is too much motion and/or image
noise and/or the running lenght is high. |
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| Export File |
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| To save the results for later analysis, it is possible to create
a file filename.drf in the "Export File" button.
The file structure is detailed here. |
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| DRF/Quantizers and Video Quality variations with different
encoders |
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| I don't know if the DRF values obtained from DivX4, 5, XVID
and DivX3files are comparable in terms of image quality. It requires
a subjective evaluation of many test samples to achieve any conclusion.
For example, in my experience, DivX5 achieve the same quality
with DRF values a little higher (ex: 2,7 -> 2.5). With the
same DRF average, a DivX4 is bigger than a DivX3 file. |
| I think that B frames have the same quality of a P frame at
the same quantizer. They just take less disk space allowing for
a lower DRF average. Both DivX5 and XVID uses an higher quantizer
for B frames in their default configuration. |
| Please send me your opinions, nfj@mail.pt. |
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| Information about DivX4
and limitations of DivX DRF Analyzer: |
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| This information is obsolete with version 0.9.2 (I had no
idea how the bitstream was constructed!) |
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| The way DRF values are stored in the video file changes
with the version of the DivX4 codec . I've only tested with
the versions 4.0 and 4.12. In the 4.0 video sample, the DRF
values were stored in the 6th byte without any bit shifting.
In 4.12 they are stored in the 8th byte with a 2 bit shifting.
Every second there is a frame where the information is bit shifted
one bit only (why?). Additionally, every keyframe has a large
constant header in both codec versions, so the information is
stored in the 27th byte with 3 bit shifting. |
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| For comparison, in a DivX3 file the information is always in
the first byte with a constant 2 bit shifting. |
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| Because of this, I cannot guarantee that DivX DRF Analyzer works
with all versions of the codec. I don't even have samples of all
versions of it. DivX 4.0 is not supported because I've not found
an easy way of unequivocally identifying the video files. DivX
DRF Analyzer version 0.9.0 only displays a warning when the file
doesn't 'look' like a 4.12 video. |
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