## MPEG2 support in VirtualDubMod

### How to open a MPEG2 file.

- Make sure the file you want to open has either the .vob (MPEG2 file) or the .txt (SmartRipper info file) extension.
- Also make sure that you have write permissions in the folder you're reading from, since VirtualDubMod will generate an index file in this folder.
- Use File/Open File as if you opened any AVI file.
- When the dialog pops up, you can either directly choose a .vob or .txt file or ease your search by selecting "MPEG (*.txt;*.vob)" in the combobox.
- Even if you do not choose "Popup extended open options", the extended options dialog will be opened. This does not occur when opening MPEG2 files with either drag'n'drop or job control. The correct aspect ratio should be selected automatically. You can however resize the image or crop those superfluous black pixels. When the video aspect is 4/3, 1.85 or 2.35, changing the width of the picture automatically changes its height. You can set it to "free" to choose height and width independently.
- What you configure in this dialog is considered as input by VirtualDubMod. This means that even if you resize the image here, you do not have to use "full processing"; "fast recompress" is enough.

### Buttons

#### Reset

Clip and Resize are reset to "zero" values. This leads in most cases to a distorted image.

#### Preview

Opens or closes a preview window so that you can see what you crop and resize.

#### Screenshot

When preview is on, output a time-stamped image in the BMP format to he output folder (chosen at the bottom of the dialog box).

#### Play

For debugging purposes. Don't click it.

#### OK

Generates the index file and maybe the audio files and then dismisses the dialog. Progress is displayed as a percentage.
The index file will be looked for the next time you open the file.
It looks like a .d2v file, but it is not, and is not compatible.

#### Cancel

Cancels file opening. On some occasions even closes VirtualDubMod (don't know why).

### Audio

Audio is treated via hard disk only (for the moment). This means that "avi audio" in virtualdubmod is useless when opening MPEG2 files.
The audio part allows to select up to 2 audio streams that will be extracted to disk.
The audio streams contain indications about language only if a SmartRipper .txt info file was used. Otherwise only bitrate and stream information are available.

#### Keep AC3

Works for formats other than AC3: the stream is only demuxed, not decoded.

#### Decode to PCM

The stream is decoded to PCM (the most common output is 16-bit stereo at 48000 Hz).

#### Dolby Surround Downmix

When the stream is decoded to PCM, you can choose to create a stereo stream containing Dolby Surround information, that can be decoded by an adequate "3D" sound card or an external compatible amplifier to produce surround effects.

### MPEG2 performance

For the best performance when using MPEG2 input, choose fast recompress (if you don't need VirtualDub's filters). The color space can be YUY2 (not bad) or YV12 (faster, same quality) depending on some factors : YV12 is not available

- when horizontal resizing is on, or
- for bilinear resampling, when width is not a multiple of 16, or
- for bicubic resampling, when width is not a multiple of 8, or
- for smooth or custom bicubic

The "fastest" mode is YV12 with bilinear resampling (no resampling at all is faster, of course...)

### Future features

What I won't do :

- SSE2 optimizations (I have no P4)
- IVTC (I have no NTSC movies)
- de-interlacing (I have no interlaced movies)

What I will do one day:

- Audio streams treated as "avi audio" inside VirtualDubMod, no longer as external files.