Video with minimal loss of quality Part 2
There are special algorithms for filtering typical compressed video artifacts. Generally, any compressed video player includes post-processing of the decompressed video with such filters.
How do analog video standards work and on what principles are they based?
This question requires fundamental knowledge in the field of radio physics and engineering, and therefore a complete and detailed explanation is not included in the scope of this FAQ. In a significant simplification, the analog video signal encoding scheme of operation is as follows: the signal is transmitted in the form of timing and information components using partial quantization. The signal itself is analog, but it is divided (quantized) into lines and frames. The PAL standard (and close to it SECAM) assumes the presence of 25 frames per second, each of which contains 576 lines. The NTSC standard assumes 30 frames per second, each with 480 lines. The synchronization component carries information about the beginning / end of lines and frames. The information component carries the luminance component (Y), used in black and white television transmission, and two color components (U / V).
Capture questions
What is video capture?
Video capture is the process of converting analog video to digital format and then storing it on a digital storage medium. The most typical example of video capture is digitizing a TV broadcast or VHS cassette on a specially equipped PC.
What are the minimum system requirements for video capture?
First, you need a video capture device capable of delivering frames of a video stream at a sufficient speed in one of the standard color-coding formats. Such a device is a TV tuner or a video card equipped with a video input. There are also more expensive and “advanced” devices that can immediately compress captured video, but their consideration is beyond the scope of these FAQs.
Second, you will need enough hard disk how fast with a large capacity, capable of recording high bit rate video. So to capture video, which is then supposed to be recorded to a VideoCD (352×288 YUV12), the hard drive must be capable of recording 4MB / s (not MB!). And to capture video with the best quality analog TV broadcast (for example, from a separate DVD player via the S-Video interface, or just from the TV broadcast), you will need a disc with a recording speed over 19MB / sec.
Third, you need a really fast CPU. . Especially if, to reduce the bit rate, the video will be compressed directly during capture. The minimum CPU required is considered Pentium-II 300, however, it is difficult to achieve “comfortable” work with the captured video on any processor with a frequency of less than 550 MHz. If you use MPEG4 algorithms for compression, the best option is Athlon 800-900 (and higher) or Pentium 4, which show excellent performance in tasks of this type.
Fourth, you will need at least 128MB of RAM; otherwise, any instability in the compression rate will have a very detrimental effect on the quality of the captured clip.
In what file format are you capturing the video?
The file format depends on the software used. Today, the three most common formats are AVI, MPEG, and ASF.
AVI (Audio-Video Interleaved – a format with interleaved blocks of audio and video information) is most often used when capturing. It was developed by Microsoft to store and play videos as part of the Video API for Windows. By its structure, this format refers to “chunks”: as in WAV or MIDI, all information is packed into headers, called chunks – chunks. This allows you to record video sequences both uncompressed and with any type of compression in an AVI file. The main disadvantages of AVI are its inability to stream (stream video over networks) and the 2GB file size limitation. And if the inability to stream does not have a noticeable effect on the video capture,
The MPEG format (the name comes from the Motion Picture Experts Group, a group of specialists in compression of video sequences), unlike AVI, involves the use of one of two standard compression algorithms: MPEG1 and MPEG2. MPEG1 is used to compress video with a small frame size (less than 288 vertically) and a bit rate of about 1-2 Mbps, and MPEG2 is used for video with a large frame size (more than 288 vertically) and a bit rate of around 5-10 Mbps.
