Newbie in need of advice

[Slava]

Pardon my ignorance, but I wonder how it is possible to create DVD quality MPEGs or AVIs of a “small” size. I am told that high quality MPEG2 video capture is supposed to result in files of huge size (up to 1 GB per minute of video). Fine. I have a big hard drive. But, I have downloaded a bunch of videos of all kinds and many of them are DVD quality alright but the size is quite manageable. For example, I have one 30-minute long video of near DVD quality and it is only 190 MB. How is this achieved? Would editing a capture with Adobe Premiere, for example, allow me to compress the capture without much loss of quality?

Thanks in advance for your input.

 

[labdog]

in first part, for video, video quality increase involves file size increase. eg for a 1 minute movie the avi file size changes from 1MB (poor video quality) to 15MB & above (high quality).

in second, MPEG2 is "just" an audio/video compression process. (the MPEG2 ratio vs AVI is around 1:10)

so the size of this same AVI file compressed with MPEG2 is around 500Ko (poor video quality) to 1.5MB (high quality).

but there is a little counterpart:
obviously, when you use a compression process, you have some video quality losses but it's not noticeable if you use an high video quality setting (DVD high quality capture setting) when you capture your video.

eg with my capture card when i set it to DVD high quality capture setting, i see a very sligthly difference between the video source & the video compressed output.
& the size for the 2 hour MPEG2 file is around 4GB. (corresponding to a movie MPEG2 file)

you can now write it on a DVD (4.7Go) but this support is too expensive. (around 18$USD)

how can we decrease the movie copy cost ?

it's to use the "newest" MPEG4 compression process which decreases another time the video file size. (MPEG4 ratio around 1:6 MPEG2)
you can now write it to a CDR because its size now is around 650MB.

<i>& we can call it: DivX. </i>







if you know you don't know, the way could be more easy...

 

[Guest]

the highest quality video is curently Uncompressd .AVI 32Bit and is 42MB/Sec
This is very diferant then Mpg2.

The small .AVI files you are downloading are very far from DVD quality.

Intel / AMD - <A HREF="http://www.llnl.gov/asci/news/white_news.html" target="_new">IBM are still the best</A>

 

[labdog]

can you explain what you could do with an 2 hours AVI file (eg a movie) which traps yours 3x120GB HD ? (42*3600*2).

<i>note:
however yes, on an absolute theoretical point of view, AVI quality is the maximum you could have. (whatever the compression method you utilize (eg MPEG1,MPEG2,MPEG4), you have more or less losses.</i>


if you know you don't know, the way could be more easy...

 

[Slava]

You are the best, guys. You make a stranger feel welcome. Thanks.

Now, Re video/audio out of sync. In my case it actually does not make much sense because the higher I set the quality of video capture the better sound and video are synchronized. Video and audio get really out of sync when I reduce capture quality. Any ideas why?

Okay, I get the idea aobut MPEG-4/DiviX. My capture software defaults to MPEG1/2. Say I capture a 2-hour video and it is 5GB or so. What should I do next to convert it to DiviX to put it on a regular CD?

(I use Pentium 4 1800 MHz + 512 MB PC-800 RDRAM + Intel 850 chipset on ASUS P4T-E motherboard + an ATA100 7200 RPM IBM drive + ASUS 8200T5 Ti-500 GeForce 3 and SB-Live X-gamer)

 

[labdog]

try this site, a very interesting one for DivX. 😉

<A HREF="http://www.divx.com" target="_new">http://www.divx.com</A>


if you know you don't know, the way could be more easy...

 

[TNCoaster33]

IS there any software that I can download to get the mpeg4 level or do I have to get a new expansion card to play mpeg4 videos

 

[Tiberius13]

www.vcdhelp.com has some great tutorials on video capturing and encoding to various formats. It is a must read for anyone wanting to play around with video files (it is particular useful for letting you know what programs exist to perform each function).

Regarding audio/video sync issues. Numerous things can cause that problem. Poor editing is a common cause (you MUST cut video on keyframes or you audio sync will be lost). Also, the ATI capture cards are off in their own little world as far as the video files they create... there is something slightly off about them. The quality is great, but the problem is when you go to convert it to another format (for example, capturing to a high quality mpg through ATI TV, then trying to convert to divx using virtual dub... the source would have perfect audio sync, but the resulting divx will have an audio sync problem where the sound gets further and further out of sync the further into the video you go).

I think if you want to just make vcd/svcd (mpg) files, using ATI TV 'might' work ok for you as far as sync goes. If you are making a divx file however, I personally recommend using virtual dub to capture the original (I capture to huffy... a lossless codec - but it takes up about 8gb per hour on your hd)

ATI capture cards are the only ones I know of that have inherent sync issues whenever you convert the original capture file.

 

[labdog]

for now,
MPEG4 is not hardware implemented like MPEG2 on gc. (cf ATI 8500, ATI AIW, ...)
the unique issue is to use an utility which translates MPEG2 compression to MPEG4 compression.


you can find this kind of softwares at <font color=blue><A HREF="http://www.divx.com" target="_new">http://www.divx.com</A></font color=blue>


if you know you don't know, the way could be more easy...

 

[Slava]

It turns out that I had two capture software packages that came with my ASUS 8200T5 Deluxe - Asus DigitalVCR and Asus Live. Well, while D-VCR only captures in MPEG 1 and 2, Asus Live can capture in 20 or so formats and even in two DivX;o) "sub"-formats (Fast and Low). I tried them out yesterday. Low sux, but Fast gives excellent quality at 640x480 and minimum compression setting; and a reasonable file size (about 200 megs for 10 minutes of video) and no video/audio sync problems anymore.

Question: Software reports all dropped frames. Is frame dropping a result of compression? (If I capture uncompressed video, zero dropped frames are reported).

 

[Guest]

It's a question of data rate and dgital/Analog convertions.
You might think that it's all digital but this "digital" stuff is based on analoge compression long before the digital ones. and most of the digital compression is also based on analog stuff.

The less data rate you give, the less of the original signal you preserve, and the signal is what keep it in sync.
and it have to do lot's with sampling rates and filters.

Intel / AMD - <A HREF="http://www.llnl.gov/asci/news/white_news.html" target="_new">IBM are still the best</A>

 

[Tiberius13]

Frame dropping in your case is likely a result of your computer being overworked by the encoding. It usually is just a momentary blip and results in a dropped frame here or there. I personally consider even 1 dropped frame excessive... but you can get away with having some frames dropped.

 

[labdog]

dropped frames < 1% with MPEG2 hardware compression & 1.5Ghz cpu.


if you know you don't know, the way could be more easy...

 

[labdog]

but this "digital" stuff is based on <b>analoge compression</b> long before the digital ones. and most of the digital compression is also based on analog stuff.

on this point im not agreed.
you receive in first your input video analogic source on your capture card. the ADC (Analog to Digital Converter) converts this analogic signal to digital out:

how can the ADC converts this analogic signal if it's compressed before ?


if you know you don't know, the way could be more easy...

 

[Guest]

Analog compression.

Read the white papers about compression.
For example all this 4:2:2/4:1:1/4:2:0:3:1:1 and such.
Yes the data is saved in digital form and working on it uses matematical formulas but the idea behind lot's of it is Analog/phsic/mental.

There is more to compression then "cosin farenhofer" and macroblocks.

Intel / AMD - <A HREF="http://www.llnl.gov/asci/news/white_news.html" target="_new">IBM are still the best</A>