Q.: What is the difference between the normal MainConcept DV Codec and the DVCPRO 25/50 Codec?
A.: The normal MainConcept DV Codec can be used by every person who is editing videos. It encodes at approximately 30 Mbits/sec. Most common DV camcorders use this codec. For that reason, it is an essential tool for every amateur producer as well as for professional users.
In contrast, the MainConcept DVCPRO 25/50 is only intended and suited for high-end solutions. It can't be used by private users and customers without adequate software and hardware.
The DVCPRO 50 Codec generates DV clips for the TV broadcast area. There are only a few expensive specific camcorders and hardware which can handle this format. It offers a higher bitrate and a higher compression rate. For the typical consumer there is no appropriate or affordable hardware or software.
Q.: Does the DV Codec work with VirtualDUB, or TMPGEncPlus? If not, then does MainActor v5 or MainVision or any other of your products substitute for them?
A.: Our DV Codec works with all programs that support Video for Windows codecs and allow access to third party codecs. There are many, so it is impossible to know them all. You can download a demo (which works exactly like the full version except for a watermark which is added to every encoded clip), and see if our codec is listed in the program you desire to use.
Many other editing and compositing features are supported in MainActor v5 and MainVision. MainVision offers compositing and MainActor v5 is used for both editing and simple compositing. It can also be used for converting your clips to MPEG-2 (MainConcept's MPEG Encoder is included in both applications).
It is worth noting that Video for Windows is an old architecture first used by Windows 3.1 for Multimedia. As it is wide-spread and simple, a lot of programs use this interface. As 2D and 3D acceleration technology grew, a new system was developed: DirectX. DirectX includes DirectShow, DirectSound, DirectDraw, etc. This seems to be the standard now and will probaly remain so for the time being. We can't say whether Video for Windows will be still supported by new operating systems or if Microsoft will surprise us with a new architecture. New codecs are based on DirectX, most applications will still be compatible with Video for Windows.
Q.: Does the MainConcept DV Codec do lossless compression? My understanding is that there are two parts to DV encoding. Can it do the entropy encoding only (lossless) and skip the DCT compression (lossless)? In other words, I could edit/compress an infinite number of times without losing any data, or I could record DV and then recompress it in a different format without additional quality loss from the DV Codec.
A.: There is always a loss in Quality when you create new frames. New frames are created when you use effects (FX) or transitions on a clip. These new frames must then be calculated and produced. In this case you will have a slight loss of quality. The visible loss created is shown by the cycle ratio. For example, a ratio of 5 means, that you can recompress a DV clip 5 times without visible quality loss. Our cycle ratio is higher than the one of the Microsoft DV codec. A pure copy from a DV clip, e.g. from one DV camcorder to your hard disk and back to another DV camcorder causes no quality loss.
Q.: How can I use the MainConcept DV Codec with VirtualDub? What are the settings for audio?
A.: Choose "Video > Filter". Then select "Resize". In the window that appears, specify 720x576 for PAL. Under "Video > Compression" select our DV Codec. The "Preferences" option enables you to adjust the advanced settings. You will find the appropriate information about them in the manual of the MainConcept DV Codec.
For audio, choose "Audio > Conversion". Then, specify 48khz and 16bit stereo. As your compressor, choose "Uncompressed PCM". Now, you should be able to generate DV files with VirtualDub and our DV Codec.
Q.: What is the differnce between DV AVI Type 1 and DV AVI Type 2?
A.: DV Type 1 is the original DV AVI format. It contains audio encapsulated in compressed video frames, meaning that it has no directly accessible audio-stream.
In contrast, DV Type 2 contains an additional audio stream. It contains the same audio stream twice: as an audio stream and also encapsulated in video frames. It is not necessary to have the audio stream encapsulated (you can do this when exporting raw DV from the timeline directly to Type 2, in which case the encapsulated audio is "0" and the "real" audio is in the separate stream). The Type 2 format was created to be compatible with the VfW (Video for Windows) architecture. Older programs and operating systems used this video architecture. In these cases, Type 2 files cannot be larger than 2 GB.
Both formats can be read by DirectShow and both do not have a file limitation in general (except for those limitations which come with the file system format [FAT16, FAT32] and/or the operating system [NT4]).
Right now MainConcept can create Type 1 and Type 2 with ulimited length (Type 2 by using the DirectShow module). With Type 1 scene detection and file split (*.dzl) are possible, too. To check out which kind of DV AVI you have you can use graphedit.
You will see two different kinds of filter graphs:
DV Type 1:
[Source] -> [AVI Splitter] -> [DV Splitter] -> [DV Decoder] -> [Renderer]
******************************* ->[Sound]
First, the AVI Splitter "opens" the AVI container. Then, the DV stream is separated to a DV video stream and a PCM audio stream. The video stream needs to be decompressed by the decoder. After that it can be rendered. The audio stream can directly played back by the sound device.
DV Type 2:
[Source] -> [AVI Splitter] -> [DV Decoder] -> [Renderer]
******************** ->[Sound]
First the AVI Splitter "opens" the AVI container and separates the DV video stream from the additional PCM audio stream. This video stream (which may still contain an unnecessary audio stream) needs to be decompressed by the decoder. After that it can be rendered. The audio stream can be played back directly by the sound device.
Q.: What is the difference between fields and frames?
A.: A series of pictures in video data can be stored in different ways. To begin, we must distinguish between frames and fields.
Every video consists of a series of individual pictures: frames. The TV format PAL uses 25 frames per second. These frames are often reduced to fields. In this process the frames are divided into lines. The top field consists of even-numbered lines, and the bottom field of odd-numbered lines, so you will have 25 frames per second and 50 fields per second. The result is that the fields are temporally shifted for 1/50 seconds.
If you now reconstruct both fields to one frame again, the picture will have a temporal offset or skip in each line. This phenomenon is called Interlacing
.
On a TV monitor the picture is always interlaced, i.e. at first, there are the odd, and then the even lines. In contrast, the PC monitor only displays full frames.
There are different way to save this on a PC: - Progressive frames (only "full" frames are used, and no
fields/field information will be saved) - Frames field-based (frames will be saved, which contain
field information to make up the frames from the
individual fields. In this case the temporal component of
the fields is considered, i.e. whether top field or bottom
field is saved first.) - Field only (only fields are saved, but no field information)
The MPEG Encoder can decode all three possibilities, but will only encode options 1 and 2. You can find these options in the "Field encoding" menu in the Details settings window.
When there is video footage with field-based frames (bottom field first) - such as DV material - there are two ways of encoding it:
A) Field encoding: bottom field first
B) Whole frame
The first way generates a data stream which contains field-based frames. They include the field order: lower field, upper field, lower field etc. That means, frames will be created from both fields in the above mentioned order.
The second way generates progressive frames, which don't include field information. So, whole frames will always be created, and the frames are broken up.
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