DVD Video Compression

MPEG-2 Video

This is the DVD standard (also used by SVCD; VCD uses MPEG-1).

720x576 (for PAL) or 720x480 (for NTSC) (except as noted below)

These are the standard, uncropped DV / DVD / D1 full-resolution sizes. There are also cropped modes (704x576 for PAL, 704x480 for NTSC), which should be used if you have an analog capture card that does not include the overscan area (for more information about this check the FAQ). There are also half-resolution modes (352x576 for PAL and 352x480 for NTSC) and quarter resolution (MPEG-1) modes (352x288 for PAL, 352x240 for NTSC), which may be of interest for archival of low-quality video. If you want good quality, however, you should always use the full resolution modes (720 or 704 pixels wide, depending on your source footage).

4:3 Display or 16:9 Display (depending on footage)

The aspect ratio should usually be the same for all clips (some authoring programs won't let you use clips with different aspect ratios in the same DVD, although the DVD specification allows it). If you select the wrong aspect ratio, the image will be squashed or stretched. 16:9 is referred to simply as "widescreen" in some software, but it's important to note that there are many different widescreen formats. DVD streams use either 4:3 or 16:9.

25 fps (for PAL) or 29.97 fps (for NTSC)

A third frame rate (24 fps) is also supported by NTSC DVDs. Instead of converting the film frame rate (24 frames per second) to the NTSC video scan rate (59.94 fields per second), it's possible to use a 24 fps stream that carries a special flag that tells the DVD player to perform this conversion in real-time, during playback. This allows for some space saving and does not degrade quality in any way, but is only useful when the source is film. If you are reading this guide, chances are you're working in video, so you should always use 25 fps (for PAL) or 29.97 fps (for NTSC).

2-pass VBR

In 2-pass VBR mode, the compressor will make two passes. In the first pass, it will compress the footage while trying to keep a constant quality, regardless of bitrate. It will then use the resulting bitrate (scaled to fit within the user-selected values) to do the final encoding. This results in the best relationship between compression and quality. It is, however, rather slow. If you use CBR at 8 Mb/s, you will end up with more or less the same quality, but the compression will not be as efficient. This means that the resulting file will be bigger, and you will not be able to fit as much video into one disc. If your movie has less than 1 hour, and you don't have any use for the extra space on the disc, you should use CBR to save on the encoding time.

Fig. 3 - Rate control

You may use a higher value for the maximum bitrate (up to 9000 or so) if you're going to use compressed sound or if the DVD won't have any sound. You may want to decrease the bitrate (especially the average bitrate) if the footage you're encoding is too big to fit in one DVD. Keep in mind that the final bitrate on a DVD cannot exceed 9.8 Mb/s (including sound, subtitles, etc.), and the value you select here applies only to the video.

Generally, a value of 6000 for average and 8000 for maximum will produce good results and allow you to fit about 90 minutes into a 4.7 GB disc (assuming you will use compressed sound; if you use uncompressed sound, then you will only be able to fit about 75 minutes into one disc at that bitrate).

The spoilage values are used by the compressor to judge the quality of the resulting stream. A higher value means a lower quality will be considered acceptable. Note that the spoilage value in TMPGEnc is relative to the latest I-picture, and not to the original frame. This means that a negative value will try to refine the image if possible (at the cost of extra bitrate). This not as useful as it seems, and in some cases (ex., still images) can actually cause a subtle shimmering, as the quality actually drops slightly at the start of each group of pictures, and then goes back up. So, generally, you should leave the spoilage value for P-pictures at zero. Setting the B-picture spoilage to zero (instead of the default 20) will improve the quality (at the cost of bitrate), but generally if you want top quality you won't use B-pictures anyway, so I recommend using the default value. If you select "old type", or if you use an older version of TMPGEnc, these options will not be present.

Some authoring programs don't like files with bitrates that drop below a certain level; if this is the case with yours, set the minimum value to 2000 or higher and enable padding. Other programs don't like files where the bitrate goes beyond a certain level; if this is the case with yours, avoid setting the maximim bitrate to a value above 8000 kb/s (some old players also have problems when the video uses more than 8000 kb/s).

0 (automatic) (see below)

This is the expected size of the video decoder buffer (basically it controls how many bytes an individual frame can use). You may set this value manually, depending on the format you're encoding for (use 224 for DVD, 112 for SVCD or 40 for VCD), but the automatic setting usually works well with all formats.

MP@ML

This refers to the type of decoder necessary to read the resulting file. Using higher values may improve the quality, but will make the video incompatible with many set-top DVD players. MP@ML stands for "Main Profile / Main Level" and is the DVD standard.

PAL or NTSC

Depending on the standard you want the resulting DVD to use.

Interlace

Normally, video is interlaced. This means that odd and even lines are shown alternately, instead of simultaneously (and recorded in the same way, naturally). DVD video should generally be interlaced even if the source footage is not (there are exceptions, such as 24-fps film flagged with 3:2 pulldown, for NTSC, but if you're working with film you probably know that already).

4:2:0

This means that for every square of four pixels (2x2) there are 4 brightness samples and 1 colour sample (divided in 2 components). This is very similar to the sampling used by PAL DV (the difference has to do with the way the colour information is sampled inside that 4-pixel square, which also depends on the codec). NTSC DV uses a format called 4:1:1 where colour information is stored for (horizontal) segments of 4 pixels, instead of 2x2 squares. The "square" approach usually produces cleaner-looking images, with less colour bleed, and it's a bit of a mystery why NTSC DV uses 4:1:1 (analog NTSC is a nightmare but they could have got it right when they moved to digital). Regardless of your footage's format (PAL or NTSC), DVD MP@ML MPEG-2 always uses 4:2:0. This is the reason why PAL DV transfers to DVD much better than NTSC DV does. NTSC footage recorded in 4:2:2 (ex., Beta) does not have this problem (nor does 4:2:2 PAL, naturally).

10 bits

This controls the precision of the discrete cosine values used in the image compression (this translates the image into a series of interfering frequencies and lets the program eliminate frequencies that aren't visually relevant - this is similar to the compression used in JPEG images). Higher values results in better quality, at the expense of encoding time and file size. For very low bitrates (i.e., under 3000) you should use a lower precision, since the space used by the DC coefficients will leave the encoder less bandwidth for the remaining data.

Highest quality

The motion search algorithm is the heart of an MPEG encoder. MPEG works by dividing an image into several small areas (called blocks), and then trying to find blocks that are present (in different positions) in more than one frame (and storing only one copy of that block). Since most blocks will usually look slightly different, some extra data is still necessary to reconstruct the real image, but the more similar the blocks, the smaller those "corrections" will need to be. A better search algorithm will get better block matches, and thus achieve better compression (or better quality for the same level of compression). Despite being very slow, TMPGEnc's motion search algorithms are some of the best of all MPEG encoders, and they are responsible for its usually excellent quality. If you need faster encoding, select the High quality mode (significantly faster than highest quality) or the Motion search estimate mode (which is even faster). For certain types of footage (with simple motion), the quality can be almost identical, and it will encode much faster. If time isn't an issue, though, stick with Highest quality, since it will deal better with complex motion.

Interlace (except as noted below)

This refers to your original footage. The vast majority of video cameras records in interlaced mode. Some cameras can optionally record in a non-interlaced mode called progressive scan. If your source footage is progressive scan video, film or non-interlaced animation, select Non-interlace.

Bottom (for DV) or Top (for analog)

This setting is the source of many problems, since some systems don't say what field order they use, and some pseudo-DV systems actually capture in analog mode. The field order is set by the capture hardware, not by the editing program, so you can't change it in software without re-compressing all the footage (note that, in digital formats, the "capture hardware" is the camera, unless the video is later converted to a different format). All you can do is make sure you set this parameter right, so that TMPGEnc knows how to encode the file. If you notice your MPEG video flickers whenever there is fast movement, the most likely cause is a wrong field order setting. Note that this will only be noticeable on a video monitor or TV set; computer monitors are not interlaced, and always show odd and even lines at the same time.

4:3 Display or 16:9 Display (see below)

If source footage dimensions are the same as the output dimensions, then selecting 4:3 Display or 16:9 Display (depending on the format) for both the source and output aspect ratios will ensure that no resizing is done (which makes the encoding faster and preserves the source quality). Alternatively, you can select the n-Line mode that corresponds to the source file's format (ex., for a 4:3 PAL file captured at 720x576, select 4:3 625 line (PAL), and for a 16:9 NTSC file captured at 704x480, select 16:9 525 line (NTSC, 704x480), etc.). In older versions of TMPGEnc, the n-line modes compressed the image horizontally by a few pixels in PAL, but this problem appears to have been fixed in newer versions. Note that the 1:1 (VGA) option doesn't refer to square images, but to square pixels (the format used by most computer-generated images).

Any (see below)

If your source footage has the correct size (i.e., the same as the output size, selected in the Video tab), any method you pick will produce the same result. If the source footage has a different size, then it will be resized using the rule you define here. If you do not want the video to be resized at all, select Center. If you want the video to be stretched to occupy the entire screen, select Full screen. If you want the video to be resized in such a way that it keeps its original aspect ratio even when that's different from the output aspect ratio, select the modes marked (keep aspect ratio). If you want to convert a video clip to fullscreen without letterboxing it (by clipping the edges instead), select No margin. If you want to adjust its size manually, select Center (custom size).

Generally, if your source footage does not match the DVD resolution, it's best to resize it using an interactive program (that will show you the result immediately), and then feed the resized footage into TMPGEnc. If you resize directly in TMPGEnc you will only see the result after the compression is finished, so if you select the wrong mode you will have wasted a lot of time.

None (see below)

Normally you will not need to apply any filters, so make sure none are selected, or processing will take longer. In some situations, however, some filters may be useful. For example, Source range can be used to trim the clip, and Clip frame can be used to crop the image. As mentioned above for the video arrange method, if you apply filters in TMPGEnc you only see the result after encoding is finished. Therefore I would recommend applying all the filters you need in your video editing or compositing program (where you can see the results almost immediately) and using TMPGEnc just for the encoding.

1 (except as noted below)

I-pictures are compressed independently (using an algorithm similar to JPEG images). This means they're ideal when the image changes too much (because they don't rely on temporal compression), but take up a lot of bits. So if you use too many I-pictures, you will need an overall higher bitrate to keep the quality up. If you're using very short GOPs (under 6 frames), you may increase this value and effectively have several sequences in each GOP (see note at the end of this section). Generally, though, stick with one I-picture per GOP.

6 (use a value between 2 and 14)

P-pictures are based on previous I and P-pictures. This means they can re-use existing parts of the image and therefore take up much less bits than I-pictures. Using P-pictures lets you keep an overall lower bitrate (and indirectly use the excess to improve the I-pictures). However, P-pictures may exhibit poor quality if there are too many changes from the previous frame. The option to detect scene changes (below) will avoid this by automatically inserting an I-picture when it detects a big change between two frames. If that option is disabled, use a lower number of P-pictures (ex., 3 or 4).

1 (use a value between 0 and 3)

B-pictures are based on past and future I and P-pictures. They provide the best compression but, as with P-pictures, have problems when the image changes too much. Also, bear in mind that B-pictures cannot be based on other B-pictures, so don't use too many in a row or the image quality will suffer, especially if there are any cuts or sudden changes. B-pictures also take longer to encode, because they must search more frames for matching blocks. If you're using a high average bitrate (above 6000 kb/s or so), you can (and should) use I and P-pictures only (ex., 1 I-picture and 14 P-pictures).

15 (for PAL) or 18 (for NTSC)

These are the standard DVD limits. This option is not present in older versions of TMPGEnc. If you're using one of those versions, you will need to control the number of frames using only the three previous settings. If a GOP has more frames than the standard allows, authoring programs will usually reject the file, and some players will not be able to play it.

1 (very important)

This tells TMPGEnc to include a header describing each GOP before the actual GOP. This is required by many authoring programs. Without this option, some programs will reject the file.

Disabled (except as noted below)

If you plan to edit the MPEG file or if you're creating streams for multi-angle DVDs, then you should turn this on. Leaving it off improves the compression.

Enabled (except as noted below)

This will automatically insert I-pictures when it detects very big changes in the image. This option increases the encoding time, but not very significantly. If you enable this option, you can increase the number of P and B-pictures so that the GOP becomes as long as possible (ex., 14 P-pictures and no B-pictures, or 7 P-pictures with 1 B-picture). If for some reason you want all GOPs to have exactly the same structure (ex., authoring a multi-angle DVD), you should disable this option and use shorter GOPs to minimise problems when the scene changes. Alternatively, use the picture type setting (below) to manually mark scene changes and make sure the GOP structure matches between angles.

Disabled

This lets you define the picture type and encoding parameters for each frame in your video clip. This is a difficult and tedious process, but if you are encoding some very complex (and short) clips, it may pay off. If you are planning to create chapter points later (in your DVD authoring program) and want them to be frame-accurate, you may use this to start a new GOP at the points where you want to put the chapter marks. In older versions of TMPGEnc, enabling this setting automatically disabled scene change detection. In newer versions, the two can co-exist.

Default (except as noted below)

Quantisation matrices are a complex subject, and I won't go into much depth here. In most cases you don't need to worry about the technical details; simply select the appropriate preset from the list. TMPGEnc's Default matrix is a variation of the MPEG standard matrix that should give you slightly better quality for most types of footage. There is a third matrix included with TMPGEnc called CG/Animation that is better suited for high-contrast footage (such as cartoons or schematic animation). If you're encoding photo-realistic animation, however, you will probably get better results using the Default matrix.

Enabled (see below)

Generally, you should select this option; it will preserve the original contrast of your source footage. If your source footage is high-contrast computer-generated animation, disabling this option will ensure its brightness and saturation remain within "legal" video limits. Some DV codecs seem to automatically compensate for this difference between video signal and digital colour range, which will make the resulting output seem too dark. If you notice the MPEG file looks darker than the DV original (the difference will be something around 8%), try disabling this option and see if that corrects the problem. Sony's and Canopus's codecs seem to keep the original range when decoding (meaning this option should be enabled). I have been told that Adaptec's and MainConcept's DV codecs perform automatic range scaling when decompressing, so if you're using one of these, disable this option. If you have information regarding other DV codecs, send me an e-mail (use the menu on the left).

Enabled

This will improve the quality by minimising round-off errors. In systems without SSE support, this will also make the encoding take longer, but will produce the same results.

Disabled

Turn this on if you notice still images look blurry, or if you're encoding a slideshow. Leaving it off will improve the quality of areas with slow or subtle motion.

Disabled

If you're encoding MPEG-1 or low-bitrate MPEG-2 you may benefit from turning this option on; it will make the image lose some sharpness, but will eliminate some compression artifacts (blocks). For DVD you'll usually use a high bitrate, so you should leave this off.