3ivx MPEG-4 5.0.2 - Windows - VfW and DS Video Encoder Compression Settings


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3ivx Video for Windows (VfW) Codec and DirectShow Video Encoder
Compression Settings

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		Basic Options Encoder Modes: Single Pass - Constant Quality Single Pass - Average Bitrate Single Pass - Constant Bitrate Dual Pass - First Pass Dual Pass - Second Pass Best Quality for Bitrae Constant Bitrate for Streaming Advanced Options Force keyframe after XXX delta frames Speed VS Quality Quantizer B Frames (ASP) QPel Motion Search (ASP) Adaptive Quantization Pixel Aspect Ratio PAR Width PAR Height
		Single Pass - Constant Quality (CQ) Encodes the video in a single pass with a fixed quality. The quality is defined via a QP value. The QP (or Quantization Parameter) allows direct configuration of the video QP used. A lower QP will result in better video quality with a larger file. A Higher QP will result in lower video quality, more compression and a smaller file. The valid range for a QP in MPEG-4 is 1..31. QP=1 is normally excessive, although it does produce near lossless video. QP2 is a recommended maximum quality. QP31 is excessively low quality producing almost total blocking, as the gains after QP22 are normally limited a recommended minimum quality is QP22 Video size can not be adequately controlled or predicted when using Constant Quality mode, although quality can be. Constant Quality encoding is not suitable for streaming.
		Single Pass - Average Bitrate (ABR) Encodes the video in a single pass aiming to maintain an average bitrate. The algorithm is quite clever but can not produce the stunning video results which a dual-pass algorithm can because the encoder has no idea what video conditions will present themselves in the future. The algorithm is controlled by the Average Bitrate setting, which is in Kilobytes/Second. There are 1,024 bytes in a Kilobyte. Bitrates greater than 500 KBytes/s can be directly entered into the bitrate text field. (Bitrate Calculator) The Maximum and Minimum Quality is used for ABR encoding, but normally the default QPs (2..22) would be the correct setting. ABR encoding will be suitable for most forms of streaming, but is not a pure Constant Bitrate algorithm. *Maximum Quality (Minimum Quantizer)* The minimum Quantization Parameter to use during encoding. The lower the number the higher the maximum quality. Lowering the Minimum Quantizer will make the encoder more conservative. Valid values are 1..31. *Minimum Quality (Maximum Quantizer)* The maximum Quantization Parameter to use during encoding. The higher the number the lower the minimum quality. If the Maximum Quantizer is too low, the encoder may overshoot the specified bitrate. Valid values are 2..31.
		Single Pass - Constant Bitrate (CBR) The constant bitrate mode will react quickly on bitrate spikes, lowering the image quality of the video and dropping frames if necessary. This is ideal for Live Broadcasting and Video Conferencing where the maximum quality in an instantaneous constant bitrate is the most important concern. The algorithm is controlled by the Constant Bitrate setting, which is in Kilobytes/Second. There are 1,024 bytes in a Kilobyte. Bitrates greater than 500 KBytes/s can be directly entered into the bitrate text field. (Bitrate Calculator) *Maximum Quality (Minimum Quantizer)* The minimum Quantization Parameter to use during encoding. The lower the number the higher the maximum quality. Increasing the Minimum Quantizer will make the encoder more conservative. Valid values are 1..31. *Minimum Quality (Maximum Quantizer)* The maximum Quantization Parameter to use during encoding. The higher the number the lower the minimum quality. Raising the Maximum Quantizer may cause the encoder to drop more frames. Valid values are 1..31.
		What is Dual Pass? Dual Pass encoding allows the encoder to produce the best possible video by performing two passes during encoding. On the first pass the encoder analyzes the video and collects detailed statistics. On the second pass the encoder uses the statistics from the first pass to make better coding decisions and to distribute the bitrate appropriately over the entirety of the video clip. After the first pass encode you may do as many second pass encodes as necessary (i.e. at different bitrates). It is important to not change the video framerate or resolution between passes. The source video and Advanced Options must be the same for both passes.
		Dual Pass - First Pass The Log File is where the statistics will be recorded in the first pass and read from in the second pass If you will be encoding more than one video at the same time remember to use a different log file for each video. You can choose to output video in the first pass, but as the encoded video will be large, video output is normally disabled to avoid filling a users hard drive. Fast First Pass Fast First Pass performs and approximated fast first pass that is significantly faster that a normal First Pass encode. Recommended.
		Dual Pass - Second Pass A Log file was recorded during the First Pass and must be selected. *Dual Pass - Best Quality for Bitrate* Dual Pass Best Quality encoded video will normally have the best quality and most accurate bitrate. The encoder attempts to find the highest possible average quality and encodes the video to maintain that quality. The algorithm is controlled by the Dual Pass Bitrate setting, which is in Kilobytes/Second. There are 1,024 bytes in a Kilobyte. Bitrates greater than 500 KBytes/s can be directly entered into the bitrate text field. (Bitrate Calculator) *Dual Pass - Constant Bitrate for Streaming* Dual Pass Constant Bitrate encoding allows the encoder to produce video as close as possible to a Constant Bitrate by performing two passes during encoding. The average bitrate will sometimes be less than requested because the encoder will not accumulate gains from frames which did not require the full constant bitrate. This is to enable successful streaming. The algorithm is controlled by the Dual Pass Bitrate setting, which is in Kilobytes/Second. There are 1,024 bytes in a Kilobyte. Bitrates greater than 500 KBytes/s can be directly entered into the bitrate text field. (Bitrate Calculator) Credit Suppression is not available for Constant Bitrate encoding. *Suppress last ... frames to ... %* The specified frames (counted from the end) will be encoded at a lower bitrate (based on the Suppression Ratio). This can be used for encoding credits, which traditionally use a lot of bits. *Suppression Ratio* The suppression ratio specifies the final size of the suppressed frames relative to what they would normally be. Lower percentages result in smaller credits and 100% effectively disables credit suppression.
		Advanced Options - Encoding Features Advanced Options can result in poor performance or results if used incorrectly. *Force keyframe after ... delta frames* In normal operation the encoder will insert keyframes for scene changes or where a keyframe would result in a more efficient encode. But in order to promote random access it is sometimes necessary to insert keyframes more regularly. The codec will insert a keyframe if it has outputted this many non-keyframes in a row. By setting this value to 0 you can produce an all keyframe video, which could be useful for an editing format, similar to DV. Keyframes are also useful for streaming broadcasts, as a user can normally only begin watching a stream after receiving a keyframe, if the stream was 25fps, and keyframes were only inserted after 250 frames (worst case) then the user might have to wait 10 seconds before seeing the stream (worst case). 300 is the default value for normal video tasks, for streaming we recommend a keyframe every 5 seconds (fps times 5). Speed VS Quality Slider Best Quality is also slowest speed. Best Quality delivers approximately 10% better quality than Better Quality mode and requires approximately 40% longer encode time. Best Quality is reccomended when time is available. *Quantizer* Different Quantizers can be used when compressing video. The default Quantizer is the H.263 Quantizer, and results in good compression with a mild smoothing of the image. The MPEG-4 alternative Quantizer produces videos which are normally slightly sharper, but can exhibit blocking artifacts at high QPs and will normally require more bitrate. MPEG Quantization is not part of the Simple Profile and thus will force the output of Advanced Simple Profile video. Advanced Simple Profile video in an MP4 file can not be opened by a Simple Profile Decoder, like QuickTime 6. Custom Quantizer (ASP) is similar to the MPEG Quantizer except that custom Inter and Intra quantization matrices can be specified using the 'Customize Matrix...' button. Custom Matrices are an expert setting and beyond the scope of this documentation. More... *B Frames* (ASP) Enables auto-insertion of Bi-directionally predicted frames (B Frames). B Frames can improve comression efficiency but causes issues with decoders other than 3ivx. *QPel Motion Search (ASP)* Enables Quarter Pixel motion search, increases acuracy but causes issues with playback on decoders other than 3ivx and is significantly slower. *Adaptive Quantization* A feature which can dramatically improve the efficiency of the codec (resulting in smaller files which look better) by varying the quantization of the video on a block by block basis based on perceptual cues. Adaptive Quantization works best with Constant Quality encoding to reduce the file size without dramatically reducing the quality. Adaptive Quantization also works well with Single Pass bitrate controlled encodes (CBR and ABR). During a Dual Pass encode the Adaptive Quantization setting has no effect. Pixel Aspect Ratio Pixel Aspect Ratio is the ratio of a pixel's width to its height. The Pixel Aspect Ratio (PAR) setting allows the encoding of anamorphic videos. An anamorphic video is video where the pixels are not square. The PAR List Box can be used to configure the PAR of the pixels encoded. Normal computer pixels are square pixels (1:1 PAR). DVDs and other video sources tend to use non-square pixels and will either need their pixels scaled to square pixels before encoding, or the pixels can be encoded, but have their PAR set. The PAR menu lists Square Pixels, the 4 common Video PARs (as found in DV and DVD sources), as well as the SVCD PARs. There is also an extended option which can be used to specify virtually any PAR. The 3ivx decoder only decodes non-square PARs correctly when playing an MP4 file, so the bitstream must be muxed into an MP4 File for the effect to be realized. Not all MPEG-4 decoders currently support PAR, thus they might produce the wrong aspect. Cropping the pixel matrix will not affect the PAR. The default is Square Pixels. More In-Depth information about PAR and why it is useful is available here. *PAR Width* Specifies the relative width of a pixel when using Custom PAR (1..255). The default is 1. PAR Height Specified the relative height of a pixel when using Custom PAR (1..255). The default is 1.

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