Originally Posted by the1too
The great picture quality of EP seems to have dupped me into the resolution-only theory. There may be high compression between XP and LP, but I'm not sure about this when comparing EP. Since XP has about 4 times more resolution by area than EP, but 6 or 8 times more capacity---then EP8 seems to have only a compression factor of 2 (8/4) which is no worse than SP. LP may have a lot of compression but this does not appear to be the case with EP.
You are throwing around some terminology (e.g., high compression/resolution by area/compression factor) in a manner that confuses me and may be causing some confusion on your end.
Let's start with the basics again - the following applies specifically to Panny recorders but can also be generally applied to other manufacturers
All Panny recorders use Variable Bit Rate mpeg2 recording and record DIGITAL audio in either uncompressed PCM (user selectable for XP mode only) or compressed constant bitrate Dolby Digital 2.0 aka AC3. COMPRESSION is DIRECTLY related to BITRATE as follows.
XP mode is 1-Hour Mode with an avg bitrate of about 8+ Mbit/sec. This is the LEAST COMPRESSED quality mode available (i.e., highest bitrate available). Resolution on the latest Pannys for this mode is 720x480 (Full D1) and used to be 704x480 for pre-2006 Panny recorders.
SP mode is 2-Hour Mode with an avg bitrate of about 4+ Mbit/sec. This is the SECOND LEAST COMPRESSED quality mode available. Resolution for this mode on the latest Pannys is 720x480 (Full D1) and used to be 704x480 for pre-2006 Panny recorders (i.e., same as XP).
LP mode is 4-Hour Mode with an avg bitrate of about 2+ Mbit/sec. This is the SECOND MOST COMPRESSED quality mode available. Resolution for this mode on the latest Pannys is 720x480 (Full D1) and used to be 704x480 for pre-2006 Panny recorders (i.e., same as XP and SP). On Pre-2005 Pannys the resolution of this mode was 352x480.
EP mode is 6/8-Hour mode with an avg bitrate of about 1+/1.5 (8/6-hr mode) and is the MOST COMPRESSED mode (i.e., lowest bitrate available) and is recorded at a resolution of 352x240. The higher 8 hour mode is achieved by lowering the constant bitrate of the AC3 digital audio stream which allows Panny to not have to lower the EP video bitrate all the way to half of the LP mode bitrate.
Higher compression (i.e., lower bitrate) allows more minutes of video content to be squeezed onto a fixed disc capacity such as a standard DVD.
The quality modes are DIRECTLY related by their proportionate bitrates only. The fixed resolutions for the various modes only determine how many bits are available per pixel to render the image. For a given FIXED BITRATE a lower (by half) resolution such as going from 704x480 to 352x480 DOUBLES the number of bits available per pixel. Trading off resolution for bitrate is a way encoders can compensate for lower bitrates to mitigate digital artifacts such as macroblocking that typically occur as COMPRESSION INCREASES with DECREASING BITRATE. This is a game of diminishing returns as there is some point wherein you cannot continue to decrease resolution to compensate for the lowering bitrate. The image becomes too blurry and cannot mitigate the high compression artifacts. AFAIC - this occurs well before you get to EP mode (i.e., I personally consider EP mode unwatchable). The above paragraph is somewhat of an oversimplification for the purpose of illustrating key points such as the relationship between COMPRESSION, BITRATE, and RESOLUTION. Other factors such as noise suppression, encoder algorithm, and quality of the source material all cause variations to some degree.
Hope this helps to clarify things and doesn't just add to the confusion.