Also known as compressor, this is a module or algorithm to compress data. Playing that data back requires a decompressor, or decoder.

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.

LEAD H264 Encoder User Interface (4.0)

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The Encoder property page provides a user interface for changing the filter's attributes.

Changes will be applied only when the filters state is stopped with the ability to set them permanently by selecting Apply or OK, or abandoning them by selecting Cancel. Positioning the mouse pointer over a control displays the general information for that control. The property page is shown in the figure below:

The following table shows the controls and their descriptions:

Control	Description
Quality Driven radio button	If this button is selected, a quality factor, set in the Quality Factor edit box, determines the video quality. A Quality Factor of 1 gives the highest quality and the largest video file size. A Quality Factor of 49 gives the smallest file size with low video quality. The default is 28.
Quality Factor edit box	Value that determines the video quality if the Quality Driven radio button is selected.
Rate Driven radio button	If this button is selected, the compression level is constant and the storage requirements can be easily predicted. However, the quality of more dynamic scenes or those with more picture detail may be affected. The associated bit rate describes the amount of data used/transferred within a time period. It is directly related to the compression level. The higher the bit rate, the lower the compression and the better the quality. The bit rate can be adjusted using the Bit Rate edit box in Bits Per Sec.
Bit Rate edit box	Value that determines the bit rate if the Rate Driven radio button is selected.
CABAC (Arithmetic Coding) radio button	Sets the entropy coding mode to Context-based Adaptive Binary Arithmetic Coding (CABAC). CABAC gives better compression at the same quality but is a little bit slower than CAVLC.
CAVLC (Huffman) radio button	Sets the entropy coding mode to Context-Adaptive Variable-Length Coding (CAVLC). CABAC gives better compression at the same quality but is a little bit slower than CAVLC.
Output Format drop-down list box	Selects the output format. Possible values are as follows:
	Value	Meaning
	Auto	Allows the LEAD H264 Encoder to determine the appropriate format.
	Main Profile (h264)	Uses MEDIATYPE_Video and MEDIASUBTYPE_h264 Generate Main profile video in which NAL units are prefixed with 00 00 01 start codes. This format is suitable for use in MPEG-2 containers.
	Main Profile (avc1)/ Flash	Uses MEDIATYPE_Video and ISOMEDIATYPE_avc1 or MEDIASUBTYPE_avc1 Generate Main profile video in which NAL units are prefixed with NAL unit length (no start codes). This format is suitable for use in ISO/MP4 containers (for iPod/iPhone/iPad/Flash).
	LEAD (L264)	Uses MEDIATYPE_Video and MEDIASUBTYPE_L264 or MEDIASUBTYPE_LX64
	iPod (avc1)	Uses MEDIATYPE_Video and ISOMEDIATYPE_avc1 or MEDIASUBTYPE_avc1 The LEAD H264 Encoder will use the appropriate setting to produce video files that can be played on iPod devices.
	PSP (avc1)	Uses MEDIATYPE_Video and ISOMEDIATYPE_avc1 or MEDIASUBTYPE_avc1 The LEAD H264 Encoder will use the appropriate setting to produce video files that can be played on PSP devices.
	Baseline Profile(h264)	Uses MEDIATYPE_Video and MEDIASUBTYPE_h264. Generate Baseline profile video in which NAL units are prefixed with 00 00 01 start codes. This format is suitable for use in MPEG-2 containers. Video uses only I and P frames (B frames are not allowed in Baseline profile).
	Baseline Profile(avc1)	Uses MEDIATYPE_Video and ISOMEDIATYPE_avc1 or MEDIASUBTYPE_avc1. Generate Baseline profile video in which NAL units are prefixed with NAL unit length (no start codes). This format is suitable for use in ISO/MP4 containers (for iPod/iPhone/iPad/Flash). Video uses only I and P frames (B frames are not allowed in Baseline profile).
	Main Profile(RTP Packetized)	Uses MEDIATYPE_Stream and MEDIASUBTYPE_h264. Generate Main profile video in which NAL units are packetized in RTP packets. This format is suitable for streaming in videoconferencing applications (not for saving to files).
	Baseline Profile(RTP Packetized)	Uses MEDIATYPE_Stream and MEDIASUBTYPE_h264. Generate Baseline profile video in which NAL units are packetized in RTP packets. This format is suitable for streaming in videoconferencing applications (not for saving to files).
	iPad (avc1)	Uses MEDIATYPE_Video and ISOMEDIATYPE_avc1 or MEDIASUBTYPE_avc1 The LEAD H264 Encoder will use the appropriate setting to produce video files that can be played on iPad devices.
	High Profile (h264)	Uses MEDIATYPE_Video and ISOMEDIATYPE_h264 Generate H264 video using High profile and NAL units are prefixed with 00 00 01 start codes. This format is suitable for use in MPEG-2 containers. This format is available only if libmfxsw32/64.dll is installed properly. Refer to How to Enable Hardware Compression and High Profiles in the LEAD H.264 Encoder topic for more information.
	High Profile (avc1) / Flash	Uses MEDIATYPE_Video and ISOMEDIATYPE_avc1 or MEDIASUBTYPE_avc1 Generate H264 video using High profile and NAL units are prefixed with NAL unit length (no start codes). This format is suitable for use in ISO/MP4 containers (for iPad/Flash). This format is available only if libmfxsw32/64.dll is installed properly. Refer to How to Enable Hardware Compression and High Profiles in the LEAD H.264 Encoder topic for more information.
Super Compression check box	If this check box is selected, LEAD's improvement to the H264 compression is used. This option produces very high compression and makes the encoding and decoding processes very fast. If high quality video is desired it is recommended to clear the check box. This option is recommended for video conferencing and broadcast applications where speed and size are very important and moderate quality is ok. This property is only available if the output is Auto,MainProifile (h264), Main Profile(avc1) / Flash, LEAD (L264), Main Profile(RTP Packetized) or Baseline Profile( RTP Packetized). Note: If this option is enabled, hardware compression will not be used (even if the computer is capable of hardware compression).
Output Frame Rate drop-down list box	Sets the playback frame rate, in frames per second, of the compressed video, regardless of the rate of the input stream frames. The LEAD H264 Encoder automatically adjusts the input video to match the desired frame rate. The rate is adjusted by dropping or duplicating input frames. If the selected frame rate is lower than the original frame rate, the compression will be higher. If "input framerate" is selected, the output frame rate will be exactly the same as the input frame rate. Use this selection when you don't want to change the frame rate.
No. of Ps between 2 Is drop-down list box	If Enable Set GOP check box is cleared, then option shown is No. of Ps between 2 Is for the number of Ps between 2 successive I frames.
GOP Length drop-down list box	If Enable Set GOP check box is selected, then the I frame length value can be selected from the drop-down list box. For example: GOP Length = 4, and No of Bs between 2 Ps = 1, results in IPBP... for each I frame.
No. of Bs between 2 Ps drop-down list box	Sets the number of B frames between 2 successive P frames.
Enable Set GOP Length check box	Changes the units of measure of the distance between two I-frames. Enable Set GOP Length check box is selected: drop-down list box unit changes to GOP Length <Enable Set GOP Length check box is cleared: drop-down list box unit changes to No. of Ps between 2 Is
Encoding Threads drop-down list box	The number of threads used during encoding. The maximum number of threads that can be used is 16. Using two threads with a dual core machine or 2 CPUs will increase the encoding speed significantly. Possible values are:
	Value	Meaning
	Auto	Prompts the LEAD H264 Encoder to determine the appropriate number of threads.
	1	Uses 1 thread during encoding and 1 slice per frame.
	2	Uses 2 threads during encoding and 2 slices per frame.
	X	Uses X threads during encoding and X slices per frame.
Capabilities section	Reports the encoder's capabilities. It indicates whether hardware compression and the high profiles are available. Refer to How to Enable Quick Sync Hardware Compression and High Profiles in the LEAD H.264 Encoder topic for more information. Use the check boxes in this section to disable hardware acceleration.
Enable Original Software (Does Not Support High Profiles) check box	Always selected, indicates the original software compression is always installed.
Enable Quick Sync Software (Supports High Profiles) check box	If selected, it indicates the libmfx needed for Quick Sync software encoding is installed. It also indicates High Profiles are available even if hardware acceleration is not possible.
Enable Quick Sync Hardware check box	If the Enable Quick Sync Hardware check box is selected, the encoder will use Quick Sync hardware in Intel processors if available (this is the default). If the Enable Quick Sync Hardware check box is cleared, the encoder will not use Quick Sync hardware acceleration even if it is available. This check box is disabled if the encoder is running or if the computer is not capable of Quick Sync hardware acceleration. You can not change this setting while the encoder is running (this is why the setting is disabled in this case).
Enable CUDA Hardware (Supports High Profiles) check box	If the Enable CUDA Hardware check box is selected, the encoder will use CUDA hardware acceleration in NVIDIA graphics cards if available (this is the default). If the Enable CUDA Hardware check box is cleared, the encoder will not use CUDA hardware acceleration even if it is available. This check box is disabled if the encoder is running or if the computer is not capable of CUDA hardware acceleration. You cannot change this setting while the encoder is running (this is why the setting is disabled in this case).
CUDA Info button	Click this button to display additional information regarding the CUDA capabilities. Clicking this button opens a message box that displays the number of CUDA GPU units. If there are GPU units, the message box will also display the version of the CUDA engine installed and the required CUDA version for optimal performance. If this message box indicates the installed version is less than the required version (5.5), it is recommended you install the latest driver for your graphics card from www.nvidia.com. The CUDA Info note below includes figures that display example message boxes.

I Frames and P Frames

To increase the compression performance, H264 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 H264 video stream comprises I Frames, B Frames and P Frames:

I: (Intraframe) frames. These are encoded without reference to another frame to allow for random access.
P: (Predictive) frames are encoded using the previous I (or P) frame as reference. P frames are compressed more than I frames.
B: (Bi-directional) frames are encoded using both previous and next I (or P) frames as reference and they are compressed more than both I, and P frames.

To increase the compression of H264, more B and P frames should be used. You do so using the "No. of Ps between 2 Is" and "No. of Bs between 2 Ps" options on the Encoder Property Page:

No. of Ps between 2 Is: represents the number of P frames between 2 successive I frames. All the frames between successive I frames are P or B frames.
No. of Bs between 2 Ps: represents the number of B frames between 2 successive P frames. All the frames between successive P frames are B frames.

For example if No. of Ps between 2 Is is 3, and No. of Bs between 2 Ps is 5, then the video stream looks like:

I B B B B B P B B B B B P B B B B B P &..

The distance between I frames must be a multiple of the distance between the P frames. The encoder will automatically adjust these values to preserve this relationship.

CUDA Info

If your computer has CUDA capabilities, clicking the CUDA Info button opens a message box similar to the following figure:

If your computer does not have CUDA capabilities, clicking the CUDA Info button opens a message box similar to the following figure: