Total length of source footage

If your disc will have more than one clip, enter the sum of the lengths of all clips. If you want to encode each clip with different settings, you will have to calculate the bitrate for one at a time, using the Media size or Other assets fields (described below) to decide how much space each clip is allowed to use.

Determines resolution, frames per second and GOP limit

Select the video standard that your disc will use. Only the GOP limit is shown in the output values, but other details of the video format may be used for internal calculations.

Pick a fixed format or specify the bitrate

PCM is the normal format for uncompressed sound. DVD PCM uses 48 KHz, 16 bits and two channels (stereo). VCD MPA uses MPEG-1 audio with a fixed bitrate of 224 kb/s. Most other formats (ex., Dolby Digital, MPEG audio for DVD or SVCD, etc.) can use different levels of compression. If your disc will use one of these, you should enter the bitrate manually (the actual format is not important; just the bitrate). Typical values are between 64 and 512 kb/s (normally between 128 and 384 kb/s, for stereo). Check your format's specifications for the exact values.

Number of independent audio tracks

This refers to the number of audio tracks; not to the number of channels. A 6-channel surround track counts only as one audio stream. Two stereo sound tracks count as two streams. This value is multiplied by the source length and the audio bitrate to determine how much space will be taken up by the audio (this is then subtracted from the available space to determine how much is left for the video).

Video bitrate control mode

Normally, the calculator will automatically decide, based on the computed bitrate values, whether you should use CBR or (2-pass) VBR. If for some reason you want to use constant bitrate regardless of the values, select Force CBR, otherwise leave it set to Auto.

Select the disc format or enter value manually

This is the bitrate limit allowed by the destination format, including audio, subtitles and other elements. Note that some disc formats may have specific limits for each element (ex., in SVCD discs, the video bitrate must be less than 2520 kb/s, even if you don't use audio)

Select the disc type or enter value manually

If you are using the whole disc for this movie, simply select the type of disc (if it's listed). If the type of disc you will use is not listed (ex., a 800 MB CD), use the custom field and enter the amount of free space manually. If not all the space on the disc is availabe, you can either enter only the available space in this field, or enter the full size and use the field below (Other assets) to subtract from it.

Subtitles, data files, menus, etc.

The value you enter here is subtracted from the Media size to determine the available space. Use this field to take into account other files that will be present in the disc, such as subtitles, menus or data files.

CBR or 2-pass VBR

Normally, the calculator will suggest 2-pass VBR. It will suggest CBR in two circumstances. First, when you select Force CBR in the first section of the calculator. Second, when there is enough space on the disc to make the average bitrate equal to or greater than the maximum bitrate. In this case, a VBR file would effectively be CBR, therefore it makes no sense to use the VBR mode (which takes longer to encode). If the calculator suggests 2-pass VBR with an average bitrate value that is very close (i.e., within 10%) of the maximum bitrate value, you can greatly reduce the encoding time (with a minimal loss in quality) by selecting CBR mode.

Maximum, average and minimum

The maximum video bitrate is calculated by subtracting the total audio bitrate from the maximum bitrate allowed by the disc format. Using a higher value might make the disc incompatible with many players. Using a lower value should not cause any problems. To make a DVD compatible with as many players as possible, use a value of 8000 kb/s or less (some older DVD players may have problems when the video bitrate goes beyond that value). The average bitrate is calculated by dividing the free disc space (taking the audio into account) by the project length, leaving a small safety margin (typically between 2% and 5%) in case the encoder does not stick to the value, and to allow for normal file overhead. Using a higher value might cause the resulting file to be too big to fit in one disc. Using a lower value should not cause any problems. The minimum bitrate is calculated simply as a percentage of the average bitrate. Using a different value should not cause any problems. Some programs prefer files where the bitrate never drops below a certain value (ex., 2000 kb/s). If this is the case with your authoring program, and the value suggest by the calculator is lower, increase it to that value. Note that (obviously), the minimum bitrate should always be less than the average bitrate, and the average bitrate should always be less than the maximum bitrate.

I-pictures, P-pictures and B-pictures

The calculator suggests a value for the number of pictures of each type (I per GOP, P per I and B per P), followed by a range of other possible values. For example "2 [ 0 - 5 ] " means 2 is the recommended value, but values between 0 and 5 should also produce good results (depending on the combinations with the other picture types). The values suggested by the calculator assume that you want to use consistent GOPs. In other words, the calculator assumes that the GOP structure will be the same throughout the file. Many encoders have an option to automatically detect scene changes, which starts a new GOP when it detects big changes from the previous frame. This usually improves quality but makes some GOPs different from others. Unless you have a very good reason not to (ex., creating multi-angle video streams), you should always enable this option. And, in this situation, you should use long GOPs (a long GOP is one where the total number of frames is close to the GOP limit for that format), since the encoder will automatically break them when necessary. In other words, even though the calculator suggests using 1 I-picture, 4 P-pictures and 0 B-pictures for a PAL movie with a bitrate of 9 Mb/s, if you enable automatic scene detection, then you should use a number closer to 14 P-pictures instead (ex., 12). If all this sounds too complicated, just use the suggested value; it will still result in good quality with automatic scene detection. For a longer description of picture types and GOP structure, see the TMPGEnc compression guide (use the menu on the left).

15 (PAL) or 18 (NTSC)

The maximum number of frames in a GOP (the GOP size limit) is determined by the DVD video format. If you are encoding video for a different format, alter this value to match its limit.

Video, audio, other and remaining

This area of the calculator tells you the approximate size of the files that will be created if you use the suggested settings. Normally the calculator will try to use all the available space, leaving only a small margin for safety and extras (ex., file headers, project data, etc.). The exception to this is when the average bitrate matches the limit for the format (in this situation, since the bitrate cannot be increased, some space will be left unused).