Available as an Add-on to LEADTOOLS Multimedia toolkits. |
The LEAD MPEG-2 Encoder Filter is a DirectShow® filter for compressing video data using the MPEG-2 (ISO/IEC 13818-2) or MPEG-1 (ISO 11172-2) standard. The LEAD MPEG-2 Decoder Also known as a decompressor, this is a module or algorithm to decompress data. is a DirectShow® filter for decompressing MPEG-2 video data.
MPEG-1 is the older standard and achieves higher compression than MPEG-2 (but at lower quality). MPEG-1 compression is used in VCD (video on CD).
MPEG-2 is the newer standard and has lower compression than MPEG-1 but
the quality is much better than MPEG-1. MPEG-2 is a high quality video
compression algorithm and is best suited for applications with higher
bit rates or high-bandwidth usage. The most common applications include
DVD-Videos,
SVCD and digital
TVs. The compressed
video data can be stored inside MPEG, AVI,
DICOM or Ogg
files with the option of saving the file with or without the audio data.
The DICOM
files can store MPEG-2 SD or HD
video. See "Supplement 42: MPEG2 Transfer Syntax" and "Supplement
137: MPEG2 MP@HL
Transfer Syntax" of the DICOM
specification for more information on requirements of the MPEG-2 SD or
HD video.
The compression options for the LEAD MPEG-2 Encoder can be set manually
through the encoder property page. The compression options can also be
set programmatically using the ILMMPG2Encoder interface.
Filter Interfaces |
|
Interface ID |
IID_ILMMPG2Encoder |
Input Media Types |
Type: |
Output Media Types |
Type: |
Filter CLSID |
CLSID_LMMPEG2Encoder |
Property Page CLSID |
CLSID_LMMPEG2EncoderProperty |
Executable |
LENCMPG23.dll, DSKernel2.dll |
Filter category |
CLSID_VideoCompressorCategory |
Header |
ILEncMPEG2_3.h |
Win32, x64
A MPEG-2 encoder capable of handling all resolutions, bit rates and
frame rates up to HDTV
would be too expensive for many simpler applications or hardware implementations.
Therefore, the MPEG-2 standard was subdivided into levels and profiles.
The MPEG-2 standard allows for four source formats, or Levels, to be coded;
ranging from Limited Definition (todays VCR quality), to full HDTV,
each with a range of bit rates. In addition to this flexibility in source
formats, MPEG-2 allows for different Profiles. Each profile offers a collection
of compression tools that together make up the coding system. A different
profile means that a different set of compression tools is available.
The four levels, including frame size and maximum bit rate, are defined
in the following table:
Level |
Maximum Frame size |
Maximum Bitrate |
Significance |
Low |
352x288 352x240 |
4 Mb/s |
CIF, consumer tape equiv. |
Main |
720x576 720x480 |
15 Mb/s |
ITU-R 601, Studio TV |
High 1440 |
1440x1152 1440x1080 |
60 Mb/s |
4x 601, consumer HDTV |
High |
1920x1152 1920x1080 |
80 Mb/s |
PROD. SMPTE |
Most of today's work is done at the Main Level, which is designated for standard video. Within this level, the Main profile is used for many applications. The MPEG-2 encoder will automatically adjust the level if the video being encoded is bigger than the maximum size for the current level.
To increase the compression performance, MPEG-2 uses Temporal Compression. Temporal compression is achieved by encoding only the difference between successive frames instead of the frames themselves. This means that frames cannot be considered in isolation. A given picture is constructed from the prediction from a previous picture, and may be used to predict the next picture. An MPEG-2 video stream The portion of the file holding the video data. The video data might be compressed to save disk space. The data has to be decompressed using a video decompressor before you can play (see) it. is comprised of I Frames, B Frames and P Frames:
To increase the compression of MPEG-2, more B and P frames should be used. You do so by adjusting the "I Frame" and "P Frame" options on the Encoder property page:
For example if I frame is 12, and P Frame is 3, then video stream looks like the following:
I B B P B B P B B P B B I B B P B B P B B P B B ..
The distance between I frames must be a multiple of the distance between the P frames. The LEAD MPEG-2 Encoder will automatically adjust these values to preserve this relationship.
LEAD MPEG-2 Encoder User Interface
This filter is included as part of the following modules: