Dr. DivX

Dr. DivX OSS for Windows
Original author(s) DivX, Inc.
Last release
2.0.0[1] / August 3, 2006 (2006-08-03)
Preview release
2.0.1 Beta 7[1] / February 2, 2008 (2008-02-02)
Development status Discontinued
Written in C, C++[2]
Operating system Microsoft Windows
Platform Intel x86
Size 4.3 Megabytes[3]
Available in English
Type Video converter
License Open source software (Lesser GNU Public License)
Portions are under “Dr.DivX DLL EULA” (Freeware)
Website labs.divx.com/DrDivX

Dr. DivX was an application created by DivX, Inc. that is capable of transcoding many video formats to DivX encoded video.

Version

Dr. DivX OSS for Mac OS X
Original author(s) DivX, Inc.
Preview release
2.0.1 Beta 2[1] / June 11, 2007 (2007-06-11)
Development status Stalled
Operating system Mac OS X
Size 8.1 Megabytes[3]
Website labs.divx.com/DrDivX

Original version

Dr. DivX was originally a closed source encoding application that was based upon royalty charging libraries. This version terminated at 1.06 for DivX 5.21.

OSS version

A new open source (LGPL) version was begun after DivX 6 shipped, after many complaints that the new encoder tool was inadequate. While open source, the project is currently implemented by one programmer employed by DivX, Inc. Because the original application used closed libraries, work had to begin from scratch, and the features of old Dr. DivX had to be re-added one by one.

Container

Typically the encoded video is muxed into the standard AVI media container for the widest device compatibility. However, this offers fewer features than other container formats, including the DivX Media Format introduced with version 6 of the DivX codec.

Multi-pass encoding

Multi pass, or dual pass encoding, generally takes as much as twice as long as single pass. However, enabling this mode does not cause any file output compatibility issues, and provides for a more even distribution of bits across the length of the encoded file, allocating them where they make the most noticeable difference to quality.

Quantization

Typically H.263 optimized is now recommended as the default quantization matrix with DivX encoding. In simple terms this can be described as a softening matrix, better suited to lower bit rates. In comparison, the MPEG-2 matrix, can be likened to a sharpening filter, better suited to higher bit rates.

Frame control

Various frame types are used under the MPEG-4 standard, which can be seen as fixed points, to which motion changes are referenced.

For bidirectional (B-frame) encoding the DivX codec offers two options:

Keyframes

Keyframes, are the pictures you see when you fast forward through a DVD. They are inserted by one of two methods under MPEG-4.

Resize filter

Bicubic (Normal) is the preferred option, offering superior quality to the simpler (and faster) bilinear option. Image operations such as sharpening, are typically better performed with filters, whose output are more customisable. Frame cropping, where black bars on wide screen movies are removed from the area to be encoded, can save otherwise wasted bits.

Sound

Typically the AVI files contain MP3 audio, as this is part of the baseline DivX profile. 128 kbit/s CBR is a standard audio bit rate, however 192 kbit/s offers optimal quality. MP3 offers the widest device compatibility, although it is possible to encode the files with other audio types, such as Dolby AC-3 and AAC.

The "Audio boost" feature is enabled by default in Dr. DivX OSS. It evens out sound levels to a more consistent level across the file length. On poor quality audio tracks, such as sometimes found on older films, this improves apparent audio quality.

Profiles

Profiles are used to apply a group of pre-set variables to a job. An encode can be set to produce a fixed quality, or file size, such as 699 MB (one CD). Some options are excluded from the baseline DivX profiles, to maintain wider hardware compatibility. If you wish to use these more advanced codec features, you will need to select an "unconstrained" profile option. Some more recent hardware chipsets (>2005) do support these features.

Filters

The original Dr. DivX featured VirtualDub filter compatibility. Avisynth script input compatibility was added in version 2.0.1 of the OSS version . Filter compatibility enables manipulation of the source before the codec begins compression. This may be to deliver a certain look, or more commonly to compensate for imperfections in the source files. For example, to smooth out low level MPEG-2 compression artifacts. While the DivX codec does have a pre-processing / noise reduction option, external filters generally provide more precise options, and when applied at appropriate settings, offer superior quality. However, this may be at the expense of encoding speed.

Temporal

Temporal filters are ideal for heavy noise i.e. VHS / analogue TV sources. The temporal filter should be applied first in a filter chain. They work (in simple terms) by comparing each frame to the one previous and after, and averaging the difference. Thus random noise tends to be blended out. Advanced features in some temporal filters include:

2D

2D filters are ideal for tidying up low level compression artifact noise on higher quality sources. They look only at one frame at a time, and seek to average out color patterns. If turned up too high, 2D filters tend to soften images, and lower overall detail levels.

Cartoons are known to present specific issues for MPEG-4 based codecs, and require the use of quality 2D filters to obtain effective results. Smart Smoother High Quality was developed for exactly this type of application, optimized for quality at the expense of speed.

Visual

Other common visual filters include brightness, contrast, color, sharpen, blur, cartoon, emboss, deblocking, denoising, old film restoration, and even subtitle / logo removal.

References

External links

This article is issued from Wikipedia - version of the 11/2/2016. The text is available under the Creative Commons Attribution/Share Alike but additional terms may apply for the media files.