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Discussion Starter · #1 ·
Can some wise, patient soul on this list please clarify the resolution, bitrate and file format of the following:


1. VCD


2. SVCD


3. ReplayTV's own special MPEG-2 format (i.e. what you get when you use DVArchive to pull off a show recorded on a Replay 5040 or the like).


4. DVD


I realize that these may be stupid questions, but I'm trying to learn. I understand that VCD is an MPEG-1 format, but at what resolution and bitrate? I undertand that SVCD and ReplayTV files are both MPEG-2 files, but have different bitrates, which is why you have to re-encode a ReplayTV file in order to burn a compliant SVCD from a ReplayTV source file (edited or not). I understand that DVDs (at least the ones I own) have a bitrate of like 192 or something (at least that's what my dvd player shows when I play a store-bought dvd). So if you burn a dvd from a replaytv file, you have to soup up the bitrate to make a compliant dvd?


And one more really stupid question: does bitrate refer exclusively to the *audio* tracks? I mean, for the video component, since the resolutions of all NTSC televisions (i.e. all in the US which aren't HDTV units) are the same and the frames-per-minute is the same, I guess that bitrate, being variable, must refer to the audio component.


Thanks in advance.


Sincerely,


Slow In Tulsa
 

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First, bitrate is a term that applies to both audio and video, not to mention pretty much anything that plays out over time. It's a measure of the average amount of data that's being transferred per second, usually measured in kilobits or megabits per second. For example, on a ReplayTV 4000, a medium quality file encodes video at 4Mb/s and audio at 224Kb/s. If you do the math ((4000*3600+224*3600)/2), that comes out to about 1.9GB per hour of disk space needed. Common MPEG2 resolutions are 720x480 (used in medium and high quality files, AKA D1 I think), and 352x480 (AKA half-D1, used in low quality files). There may also be 352x240, but I've never dealt with such a resolution.


I think I've covered the Replay side of things. DVDs are almost identical in spec as ReplayTV files. The maximum bitrate is a combined 10Mb/s, so usually about 9.7Mb/s for video, so all low and medium quality Replay files are in spec. High quality files seem to be, but they're encoded with a variable bitrate that simply averages 6Mb/s -- it can spike past 10Mb/s and confuse DVD players (I'm not sure on 5000s, though). The other issue with Replay-created files is that the audio format (MPEG1 layer 2) is not supported by all DVD players. For full compatibility, you'll need to reencode to either AC3 (aka Dolby Digital) or PCM (a compressd WAV file, I believe).


I can't address VCDs and SVCDs, as I've never dealt with them.
 

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Here we go...


Video-CD:

Video: MPEG-1, CBR 1150kbps

PAL: 352x288 25fps

NTSC Film: 352x240 23.976fps

NTSC: 352x240 29.97fps

Audio: Layer-2 44100Hz 224kbps



Super Video-CD

Video: MPEG-2, CBR 2520kbps

PAL: 480x576 25fps CBR 2520kbps

NTSC Film: 480x480 23.976fps

NTSC: 480x480 29.97fps

Audio: Layer-2 44100Hz 224kbps



DVD

Video: MPEG-2, CQ 65

PAL: 720x576 25fps

NTSC (North America and Japan): 720x480 29.97fps

Audio: Layer-2 48000Hz 384kbps



Dont know anything about ReplayTV.



This and other information can be found at web sites like www_vcdhelp_com (used _ instead of dots as cant post a url)
 

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By the way CQ65 = Constant quality 65 and results in a variable bitrate between 2000kbps and 8000kbps (or 2mpbs and 8 mbps)
 

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Quote:
Originally posted by Cam73
Here we go...


DVD

Video: MPEG-2, CQ 65

PAL: 720x576 25fps

NTSC (North America and Japan): 720x480 29.97fps

Audio: Layer-2 48000Hz 384kbps
Don't know much about DVD either... you gave all the different resolutions for VCD and such.


DVD is far more open, as stated previously there are several resolutions for DVD 720x480, 352x480. Nor does it need to be CQ65, VBR, CBR and in any format it can even change any of these settings on the fly!


Frame rate, your 29.97 is an output frame rate, input frame rates can be 29.97 or 23.97 with pulldown enabled.


Audio does have to be 48KHz. But, not 384kb there are several bitrates that work 192, 224, etc. Nor does it have to be MPEG-1 Layer 2, in fact it shouldn't be MPEG-1 Layer 2. It should be either PCM or Dolby Digital encoded. Not all DVD players handle MPEG audio streams correctly.


The specs for the replay formats can be found here:
http://www.molehill.org/twiki/bin/view/Replay/

(it's not up right now, but the info in there, and on this board in several places, maybe even in the FAQ)


The key thing to note, is the 5k replay goes outside the DVD 10Mbps spec at times. This can cause you problems with authoring. Most use med quality to get around this problem. Med quality seems to peak at
 
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