ILMMP42Encoder Interface
This is the interface for the LEAD MPEG-4 Encoder.
Interface Properties:
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Type |
Name |
Description | ||||||||
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long |
QFactor |
The quality factor used in compressing the 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.; the lower the quality factor, the better the quality. Possible values range from 1 (best) to 31 (worst). | ||||||||
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eQuantType |
QuantType |
The quantization method applied. Possible values are (members of the eQuantType enumeration):
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double |
OutputFrameRate |
The desired output frame rate, in frames per second. Possible values range from 1.0 to 30.0. Pass -1 to make the output frame rate the same as the input frame rate. | ||||||||
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eOutputFormat |
OutputFormat |
The encoder Also known as compressor, this is a module or algorithm to compress data. Playing that data back requires a decompressor, or decoder. output type. Possible values are (members of the eOutputFormat enumeration):
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VARIANT_BOOL |
SuperCompression |
Enables/disables super compression, LEAD’s improvement to the MPEG4 video compression. When super compression is used, compressed video size is reduced noticeably with almost the same quality, and the encoding and decoding speed is enhanced. Files generated using this option, will not be MPEG4 compliant: they can be decoded only by the LEAD MPEG4 Video Decoder Also known as a decompressor, this is a module or algorithm to decompress data.. Possible values are:
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long |
PFrames |
Specifies the number of P frames between two successive I frames *. | ||||||||
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long |
BFrames |
Specifies the number of B frames between two successive P frames *. | ||||||||
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long |
SearchWidth |
The search block width used when determining if motion is occurring. The larger the block, the slower the encoding process. It is not recommended to use large values. The range is from 2 to the video stream width, in pixels. | ||||||||
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long |
SearchHeight |
The search block height used when determining if motion is occurring. The larger the block, the slower the encoding process. It is not recommended to use large values. The range is from 2 to the video stream height, in pixels. | ||||||||
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eMotionAlgorithm |
MotionAlgorithm |
The algorithm to be used when determining if motion is occurring. Possible values are (members of the eMotionAlgorithm enumeration):
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eMotionAccuracy |
MotionAccuracy |
Motion estimation accuracy. Possible values are (members of the eMotionAccuracy enumeration):
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eMotionVectorPerMacroblock |
MotionVectorPerMacroblock |
Specifies how many motion vectors are used in the motion estimation algorithm. Possible values are (members of the eMotionVectorPerMacroblock enumeration):
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eEncodingThreads |
EncodingThreads |
The number of threads used during encoding. The maximum number of threads that can be used is 2. Using two threads with a dual core machine or 2 CPUs will increase the encoding speed significantly. Possible values are: LMP4_THREAD_AUTO: Have the LEAD MPEG4 Encoder determine the appropriate number of threads. LMP4_THREAD_1: Use 1 thread during encoding LMP4_THREAD_2: Use 2 threads during encoding | ||||||||
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VARIANT_BOOL |
InsertVOL |
Set to VARIANT_TRUE to insert a mpeg4 header before each I-frame. This is useful in a video broadcasting where the mpeg4 decoder might start decoding from the middle of the stream. | ||||||||
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VARIANT_BOOL |
InsertGOV |
Set to VARIANT_TRUE to insert an optional header before I frames that indicates to the decoder the timestamp of the I frame and whether it is open/closed GOV. This helps the stream to be randomly seeked in some decoders. However, the LEAD MPEG4 decoder does not require it. | ||||||||
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eCompressionMode |
CompressionMode |
Sets the compression mode. Possible values are: LMP4_COMPRESSIONMODE_ConstantQuality: Uses the QFactor property value to regulate the image quality. LMP4_COMPRESSIONMODE_VariableBitrate: Varies the quality over short durations. However, it will achieve an average rate matching the BitRate property value. LMP4_COMPRESSIONMODE_ConstantBitrate: Strictly adheres to the rate specified in the BitRate property. | ||||||||
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long |
BitRate |
This is the average or constant bitrate used when the CompressionMode is set to LMP4_COMPRESSIONMODE_VariableBitrate or LMP4_COMPRESSIONMODE_ConstantBitrate. The value is in bits per second. |
Methods:
|
Name |
Parameters |
Description |
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WriteToRegistry |
None |
This method writes all of the encoder settings to the system registry. The next time the encoder is loaded, it retrieves the settings from the registry and applies them. |
* To increase compression performance, MPEG4 uses Temporal Compression. Temporal compression is achieved by only encoding 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-4 video stream is comprised of I Frames, B Frames and P Frames:
I: (Intraframe) frames. These frames are also called Key Frames, they are encoded without reference to other frames and can be decoded independent of any other frame, and hence they allow random access. I frames are the largest frames in size and least compressed.
P: (Predictive) frames are encoded using the previous I/P frame as reference and can only be decoded correctly if the previous I/P is available. P frames are smaller and more compressed than I frames.
B: (Bi-directional) frames are encoded using information frame the previous I/P frame and the next I/P frame and can only be decoded correctly if the previous I/P frame and the next I/P frame are available. B frames are smaller than both P and I frames and they are the most compressed frames.
So to increase the compression of MPEG-4 more B and P frames should be used by adjusting PFrames and BFrames properties.