7.10 Video encoding

VEGA ZZ can encode video streams that the user can include in PowerPoint presentations, HTML documents, Video CD/Super Video CD/DVD medias, on-line video streaming applications, etc. At this time, it's possible to convert MD trajectories to high quality videos choosing the Save trajectory item in the File menu. When the video format is selected, the codec option window is shown:

A codec is a software component with the capability to encode and decode audio/video streams. In the Codec list, you can select the codec that will be used to encode the video stream. Each codec has specific application fields and you should select the more suitable one. As an example, if you want to perform video editing, the best choice is a codec with low compression ratio for the best quality and full frame encoding (e.g. Huffyuv, DV, M-JPEG, Lagarith). In this specific application field, you can't use MPEG-1, MPEG-2, DivX, XviD (MPEG-4) because not all frames are full encoded but some of them are compressed by difference from the previous one. The  video editing requires "single frame" precision cut,  that isn't possible when you use MPEG encoding methods.
In the Video codec information box, the properties of the selected codec are shown: the FOURCC code is a four character string used by  Windows Multimedia System to recognize and manage the codec and it's the same used in the AVI file header, Driver name is the DLL file name encapsulating the codec, Delta frame indicates if the codec supports delta frames and Format restrictions reports limits and warnings about  the codec.
The Quality slider allows to change the compression quality (high quality = low compression ratio) or the bitrate for MPEG-1 and MPEG-2 (VOB) compression. The bitrate must be correctly selected if you want obtain standard medias: e.g. if you want to create a Video CD (VCD), you must select MPEG-1 compression and 1150 as bitrate to obtain a full compliant media.
About button shows the codec copyright message and Configure button opens the codec control panel, if it's available. To configure the codec, you must consult its documentation.
In Rendering mode box, you can select the rendering method (for more information, see the Save image section).
In Resolution box, you can select the frame size only if the Hardware or the Software rendering modes are selected. It's also possible to enter custom resolutions. In the following table, the standard frame sizes are shown:

The AntiAlias option is active only if the Software rendering mode is selected and enabling it, the jagged edges are smoothed. The algorithm performs a super-sampling (4x or 16x) increasing the image size to 2x or 4x making the rendering more precise. Finally, it resizes the image to the user-defined dimension applying a smoothing pixel algorithm. The 16x AntiAlias generates better images but it requires a lot of memory.
In Frame rate box, you can select the number of frames that will be displayed for each second. If you want to obtain files t compatible with video standards, you must select the correct frame rate as shown in the following table:

About the standards: the first number is the number of scan lines (vertical resolution), the character could be i (interlaced scan) or p (progressive scan) and the last number is the field rate and not the frame rate. The interlaced scan requires two fields to build one frame and so the frame rate is half field rate (e.g. 720i50). The progressive scan requires one field to build one frame and so the frame rate is equal to the field rate.

The 4/3 aspect ratio switch forces the width and height frame ratio to 4/3. This is useful for the Super Video CD (SVCD) resolutions (e.g 480x576 and 480x480) that don't have the 4/3 aspect ratio.

Ok button starts the encoding and Cancel button abort it.

7.10.1 MPEG-1 & MPEG-2 settings

When you select MPEG-1 video stream or DVD VOB (MPEG-2) as output file, the Configure button is active and clicking it, the MPEG settings are shown:

In Bitrate box, you can activate the Variable bitrate encoding (preferred to the constant bitrate encoding for the better quality and the better compression ratio), the High quality mode, the automatic maximum bitrate selection (Auto max bitrate, not all DVD players support the high-bitrates selected by the algorithm. For better compatibility, it shouldn't activated) and the maximum bitrate in kilobits per second (Max bitrate, this field is disabled if Auto max bitrate is checked). The GOP (Group Op Pictures) box contains parameters about the GOP structure. The MPEG encoding is based on special frames called I-frames, B-frames and P-frames (for more information about the MPEG standards, see http://www.chiariglione.org/mpeg). The periodic pattern of frames resulting from the combination of I, B and P frames is called GOP (e.g. IBBPBBPBBPBB). The GOP size is the GOP length. The standard values are 12, 15 (PAL) and 18 (NTSC). The Max B-frames filed allows to specify the maximum number of contiguous B-frames (e.g. 1 IBPBPBPBPBPB, 2 IBBPBBPBBPBB) and it must be a number from 0 to 4. Checking Force closed GOP, the GOP structure will be terminated with a P-frame, reducing the GOP size subtracting the Max B-frames value. This option is useful if you want edit the stream using external software. In  Aspect ratio box, it's possible to choose the pixel width/height ratio that will be used playing the stream. The Advanced settings are only for expert users: they allow to enable the Trellis quantization, the Extreme & slow settings, the Interlaced encoding (MPEG-2 only), the field order in the interlaced scan (Top field first) and the automatic Scene detection. In the Profiles box, you can select pre-defined settings in order to simplify the encoder configuration (Default, Digital Versatile Disk (DVD) NTSC, Digital Versatile Disk (DVD) PAL, Super Video CD (SVCD) NTSC, Super Video CD (SVCD) PAL, Video CD (VCD) NTSC and Video CD (VCD) PAL). Not all options are accessible at the same time, because DVD and SVCD require MPEG-2 encoding and VCD requires the MPEG-1. The profile selection changes the settings in Codec configuration dialog also (e.g. Resolution, Frame rate and 4/3 aspect ratio), but remember that the resolution is not changed if the Snapshot rendering mode is selected.

WARNINGS:
At this time, VEGA ZZ isn't able to produce MPEG-1 files VCD full compliant, because the encoding algorithm doesn't use a real constant bitrate (CBR) inserting fluctuations in the bitrate value. This is not a real problem for the modern DVD players.

7.10.2 Video formats

The following table show the most common video format that you can use to realize full compliant medias:

7.10.3 How to obtain the codecs

The recommended codecs are all free and available as shown in the following table:

The YUV only codecs aren't supported by VEGA ZZ because it uses the 32 bit RGBA color space.

7.10.4 Recommended tools

• VirtualDub (http://www.virtualdub.org)
  VirtualDub is a video capture/processing utility for 32-bit Windows platforms (95/98/ME/NT4/2000/XP), licensed under the GNU General Public License (GPL).  It lacks the editing power of a general-purpose editor such as Adobe Premiere, but is streamlined for fast linear operations over video.  It has batch-processing capabilities for processing large numbers of files and can be extended with third-party video filters.  VirtualDub is mainly geared toward processing AVI files, although it can read (not write) MPEG-1 and also handle sets of BMP images.
   

• Media Player Classic (http://sourceforge.net/projects/guliverkli)
  Media Player Classic (MPC) is an extremely light-weight media player for Windows. It looks just like the good-old Media Player v6.4, but has lots of nice extra features. MPC has, for instance, a built in DVD player with real-time zoom and built-in MPEG-2 decoder, support for AVI subtitles, QuickTime and RealVideo support (requires QT and/or Real player), and lots more.
   

• Media Player Classic Home Cinema (http://mpc-hc.sourceforge.net)
  It's a project based on the old Media Player Classic with some improvements.