From the Zoran PR:
"SoftDVD is capable of playing 24 frame per second encrypted movies at full frame rate using Intel's latest Pentium II processors, even when running 8.0 Mbit/sec variable bit rate DVD files."
From the DVD FAQ.
videodiscovery.com
A disc has one track (stream) of MPEG-2 constant bit rate (CBR) or variable bit rate (VBR) compressed digital video. A restricted version of MPEG-2 Main Profile at Main Level (MP@ML) is used. SP@ML is also supported. MPEG-1 CBR and VBR video is also allowed. 525/60 (NTSC, 29.97 interlaced frames/sec) and 625/50 (PAL, 25 interlaced frames/sec) video display systems are expressly supported. Coded frame rates of 24 fps progressive from film, 25 fps interlaced from PAL video, and 29.97 fps interlaced from NTSC video are typical. In the case of 24 fps source, the encoder embeds MPEG-2 repeat_first_field flags into the video stream to make the decoder either perform 3-2 pulldown for 60 (59.94) Hz displays or 2-2 pulldown (with 4% speedup) for 50 Hz displays. In other words, the player doesn't really "know" what the encoded rate is, it simply follows the MPEG-2 encoder's instructions to produce the predetermined display rate of 25 fps or 29.97 fps. (No current players convert from PAL to NTSC or NTSC to PAL. See 1.19.) It's interesting to note that even interlaced source video is usually encoded as progressive-structured MPEG pictures, with interlaced field-encoded macroblocks used only when needed for motion. On a computer, which is not tied to the display refresh rate, the repeat_first_field flags are mostly ignored and the video is shown as progressive frames at the original rate. Computers can also improve the quality of interlaced source by doubling fields and displaying them as progressive frames at twice the normal rate.
See the MPEG page for more information on MPEG-2 video.
Picture dimensions are max 720x480 (29.97 frames/sec) or 720x576 (25 frames/sec). Pictures are subsampled from 4:2:2 ITU-R 601 down to 4:2:0, allocating an average of 12 bits/pixel. (Color depth is still 24 bits, since color samples are shared across 4 pixels.) The uncompressed source is 124.416 Mbps for video source (720x480x12x30 or 720x576x12x25), or either 99.533 or 119.439 Mbps for film source (720x480x12x24 or 720x576x12x24). Using the traditional (and rather subjective) television measurement of "lines of horizontal resolution" DVD can have 540 lines on a standard TV (720/(4/3)) and 405 on a widescreen TV (720/(16/9)). In practice, most DVD players provide about 500 lines because of filtering. VHS has about 230 (172 w/s) lines and laserdisc has about 425 (318 w/s).
Different players use different numbers of bits for the video digital-to-analog converter. (Sony and Toshiba use 10 bits, Pioneer and Panasonic use 9 bits.) This has nothing to do with the MPEG decoding process. It provides more "headroom" and more analog signal levels which supposedly give a better picture.
Maximum video bitrate is 9.8 Mbps. The "average" bitrate is 3.5 but depends entirely on the length, quality, amount of audio, etc. This is a 36:1 reduction from uncompressed 124 Mbps (or a 28:1 reduction from 100 Mbps film source). Raw channel data is read off the disc at a constant 26.16 Mbps. After 8/16 demodulation it's down to 13.08 Mbps. After error correction the user data stream goes into the track buffer at a constant 11.08 Mbps. The track buffer feeds system stream data out at a variable rate of up to 10.08 Mbps. After system overhead, the maximum rate of combined elementary streams (audio + video + subpicture) is 10.08. MPEG-1 video rate is limited to 1.856 Mbps with a typical rate of 1.15 Mbps. |
