is it real hows it done??????
Willen wrote:DVD (Digital Versatile Disc)
Uses a disc similar in physical size to a CD, and at first glance can easily be mistaken for one, but has the capacity to hold up to 17.1GB of data on a dual-layer double-sided disc. The more common recordable dual-layer single-sided versions hold up to 8.5GB of data. I've never seen a recordable 17.1GB DL/DS disc, although it is possible for a manufacturer to produce one. A single-layer, single-sided DVD will hold 4.7GB (4.3GiB), or the equivalent of about 7 CDs.
MPEG-2 is used for encoding video and audio can be recorded as uncompressed Linear PCM, MPEG-1 Audio Layer II (MP2), Dolby Digital (AC3), or DTS. Normal video resolutions are 720x480, 29.97 fps for NTSC and 720x576, 25 fps for PAL, 16:9 or 4:3 aspect ratio, up to 9,800 kbps. Additional available NTSC video resolutions are 704x480, 352x480, and 352x240. PAL resolutions also include 704x576, 352x576, and 352x288. Optionally, you can use MPEG-1 for video (up to 1,856 kbps) using the same VCD standards (see above). Audio is 48 or 96 kHz (PCM, DTS), 16 or 24 bits for PCM, and can contain up to 7.1-channels. Multiple audio tracks are possible.
Even then, without going out of the DVD specs too wildly, you can safely record about 10 hours (at EP) of video on a double-layer DVD and have it play on a stand-alone player. This is compared to the normal 3.5 hour capacity (at SP) of a 8.5GB disc. Longer times are possible with certain source materials and encoder settings without major playback issues. Of course, at these long playback times, the video (and audio) quality must be compromised to reach these capacities. This means lower quality (resolutions and bit rates). Single-layer 4.7GB DVDs will obviously hold less - 6 hours (at EP) is the typical maximum.
Now, if the DVD is used to store video files (AVI, DIVX, MKV, MP4, MPG, WMV, etc.), then if the resolutions and bit rates are low enough, it may be possible to cram 175 hours of video on a single disc (especially if it is a double-layer DVD). But the video quality would probably be lower than the typical VCD and definitely lower than that of a SVCD or DVD. I'm not willing to encode 175 hours of low resolution, low bit rate video to find out if the claims of VCD quality are true.
If you really need to know how is it done, then ask the owner of the 'VCD'. Either he will know or the person who made it for him.
The real question you should be asking is, "why would anyone want to put 175 hours on one disc?"
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