TMPGEnc Settings (Video)

The Setting dialog box allows you to alter the encoder parameters. It includes the following tabs:

• Video
• Advanced
• GOP Structure
• Quantize Matrix
• Audio
• System

Video

Stream type

Select from one of the following:

Size

This option sets the size (resolution) of the video pictures that you are encoding to in pixels across the screen by number of lines.

If you are encoding a VCD then you must set these values to 352 by 240 (for NTSC) or 352 by 288 (for PAL).

For SVCD choose 480 by 480 for NTSC or 480 by 576 for PAL.

Aspect ratio

This is the ratio of width to height that the encoded video will be. This information is present in the output video stream and used by the decoder to display the video at the correct aspect ratio. The following settings are possible:

Frame rate

This is the number of video frames (complete pictures) that will be presented to the viewer each second. When producing MPEG streams for playback on TV it is important to get these numbers correct. Remember that TVs use interlacing to give twice as many fields per seconds as frames per second, so PAL TV has a frame rate of 25fps, NTSC TV has a frame rate of 29.97.

When playing back on a PC, any frame rate can be used. Lower frame rates will require less bits to encode, but will show jerkier motion.

Rate control mode

This option allows you to choose the type of bitrate control you wish to use. The bitrate control varies the bitrate of the video stream, depending on the options you choose. Different control modes have advantages and disadvantages over one another.

If you are creating an XVCD or SVCD, the bitrate calculator will help you determine the optimum bitrate for encoding your video.

Constant bitrate (CBR)

The video stream bitrate is fixed to a constant value. This means that high motion scenes are allocated the same number of bits as low motion scenes. Either bits are wasted during the encoding of low motion scenes, or block artifacts will be seen during high motion scenes.

Use this setting to create a VCD.

2-Pass variable bitrate (VBR)

Variable bit rate does exactly what it says on the tin - the bit rate is varied. During periods of high motion the number of bits used to encode the video is increased. When the action stops the number of bits used to encode it is reduced. This gives the best video quality for the least average number of bits.

To work out which parts of the video should be allocated the most bits the encoder processes the whole video clip twice (hence the "2-pass" part of the name). During the first pass it keeps a record of the complexity of each frame. Highly complex frames will be allocated more bits. The second pass does the actual encoding.

Use this setting to create high quality SVCD of DVD videos automatically.

Manual VBR (MVBR)

This setting allows you to manually select different bitrates for different scenes of your video. This is done using the "Force picture type setting" option on the "GOP structure" tab. The video bitrate remains constant between your manual settings, so its more like CBR than VBR.

Only use this setting if you have problems encoding short, tricky video sequences and have a lot of time to spend fiddling with the manual settings.

Automatic VBR (CQ_VBR)

Constant Quality (CQ)

Setting

The "Setting" button opens up the variable bitrate setting dialog box. Depending on the Rate control mode setting, this dialog box has different fields to fill in.

Constant bitrate (CBR)

2-Pass variable bitrate (VBR)

Manual VBR (MVBR):

Automatic VBR (CQ_VBR) and Constant Quality (CQ):

Bitrate

This field is only active when CBR is selected. It allows you to specify the bitrate without opening the Setting dialog box.

VBV buffer size

This value specifies the size of the decoders "Video Buffering Verifier". It represents the amount of coded video data that can be buffered by the decoder. At constant bitrates the buffer allows best use of the MPEG compression techniques. It is filled at a constant rate (that of the video stream) and partially emptied when a frame is decoded. The buffer fills up during sequences that compress well and empties during sequences that do not compress well.

Usual values are 40 for producing an MPEG-1 VCD and 112 for an MPEG-2 SVCD. These are the minimum allowed by the specifications, but if you are encoding for a particular player it may have a larger VBV buffer, so these could be increased (producing XVCD or XSVCD discs).

Profile & level

The MPEG-2 specification defines a number of profiles and a number of levels. The most commonly used combination is Main Profile at Main Level (MP@ML). MP@ML is used for the VCD, SVCD and DVD standards.

Unless you know what you are doing, leave this alone.

Video format

Set the video format to that of your source material.

Encode mode

This allows you to select how the video will be decoded on playback. Choose from the following options.

YUV format

This allows you to specify the precision with which the luminance (brightness information) and chrominance (colour information) signals are encoded. The eye is more (spatially) sensitive to brightness changes than colour changes, therefore fewer chrominance samples than luminance samples are required.

MP@ML only allows the use of 4:2:0. Unless you know what you are doing leave this set to 4:2:0.

DC component precision

The DC component represents the average brightness of a block (8x8 pixel region). In MPEG-1 video this is fixed to 8 bits, but MPEG-2 allows higher precision. It is important that the DC component is accurately represented, so a setting of 10 is recommended for MPEG-2 sequences, unless you are encoding using a low bitrate.

Motion search precision

Select the precision with which the encoder tracks movement between consecutive video frames. The better the search, the longer it will take. I tend to choose either "High Quality". Many people report that "Highest Quality" provides no visible improvement, but dramatically increases the encode times. Use low quality settings only for test runs or if you have a very slow PC.

Digital Video
Glossary MPEG Bitrate

Video Editing
Intro

HDTV
Introduction Plasma LCD Projection HDTV Antennas

Freeview
Introduction Aerial Channels Coverage PVR Recording STB Guides TV

Media
VCD SVCD DVD DV

TMPGEnc
Beginners Settings

Encode

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MHEG-5

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