With how many bit rate increase i will see a difference ?

[bambam]

Let's say we have a mpg file at a bit rate of 2000 kbps
approximatly how many more or less bitrate i must add or cut for my human eyes to see a difference ? is it 100, 200 500 ?

[sacajaweeda]

If your source is mpeg, the only result possible when re-encoding mpeg is degradation. You will see no improvement whatsoever no matter how high you jack up the bitrate. Period.

[bambam]

Ok yeah you're right
garbage in garbage out ...

Ok let's say i have an original avi or mpg file at a bitrate of 2000 kbps
and i have other tile with 1950 1900 1800 1700 kbs of bitrate
In which file my human eyes will see a difference with the original 2000 kbps file ?

[Gazorgan]

If you have an original MPEG at a bitrate of 2000, if you increase the bitrate to 3000 it will look worse. So the answer to your question is 1950.

Now AVI's are different, since the bitrates aren't related the same way. An AVI with a bitrate of 2000 is fairly high quality. Converted to an MPEG with a bitrate of 2000 it would look a LOT worse in the same resolution(assuming 640x480 AVI).

To answer your question correctly, we need the specs on the source file, and what the final product is supposed to be (VCD, xVCD, SVCD, xSVCD, DVD).

[bambam]

Now AVI's are different, since the bitrates aren't related the same way

Can you explain this to me because i always tought that a bitrate was a bitrate no matter if it was a avi mpg ram mov or whatever ?

[eas]

AVI is just a container format (like MOV), and doesn't necessarily imply anything about the compression scheme used, so while it is accurate to say that AVI bitrates can't be compared the same way that MPEG bitrates can, you can't necessarily say that an AVI with a given bitrate is going to look better than an MPEG 1 or 2 at the same bitrate.

However, most AVIs kicking around the net contain data that has been encoded with some sort of MPEG4 codec. MPEG4 can achieve higher quality at the same bitrates than MPEG1 or 2, this is particularly true at lower bitrates since that was the target for MPEG4 (as I understand it). At DVD bitrates with DVD res video MPEG4 probably doesn't hold an obvious edge over MPEG2, and may infact be hurt by the fact that MPEG2 has support for interlaced video.

I don't really have a rule of thumb for equating MPEG1/2 bitrates with MPEG4 bitrates. Your best bet is to get some high quality video with some high motion and high detail scenes and encode some clips using the two codecs at different bitrates and then do side by side comparisons of stills and the two clips running.

[FKrueger]

I capture at 2.0 mbps, 2.06, and 2.18, from cable for vcds, I am happy with the quality of the eyes, focus,clariety on all 3 speeds and I watch it on a 55" Pioneer. They beat tapes easily, even when recorded in the 2 hr mode. Don't know if that tells you anything since you are converting files, I am not, I capture with the AIW, burn, and delete.

[bambam]

Thank you for the information

[zak_swan]

i've been doing this stuff for a year and still feel like a newbie.

i always encode avi's or mpegs to dvd mpegs.

when i do this i always use variable bitrate and set them to: max bitrate 8000, average 3000, and min 2500

all the stuff looks ok when i play on dvd player but i always wonder if i'm using too little or too much bitrate

do those calculators help?

[sacajaweeda]

All the bitrate calculators will tell you is how high a setting you can use and still fit it on a disc. Quality will vary from clip to clip, too many variables.

[zak_swan]

so how do u figure out what bitrate to use when encoding?

[Capmaster]

Bitrate's a subjective thing. Everyone will have a different preference. I cap my VHS at a minimum of about 4 Mbps average with a peak of about 5. That's only if I have to fit more than 2 hours on a DVD and it doesn't have too much action. Ideally I like to cap at between 6 and 7 average with a peak of 8 or 9 Mbps. I usually capture MPEG2, VBR, full D1, NTSC, Layer 2 audio.

[WuphonsReach]

so how do u figure out what bitrate to use when encoding?

Cheat sheets, or online bitrate calculators (or downloaded bitrate calculators... which I bet you'll find on the left).

I do a lot of TV to DVD. Once you strip commercials, there is 48min of footage per hour show. If I do it as 720x480, 6000kbps and 256kbps AC3 audio allows me to fit 2 eps per disc. 352x480 and 3800kbps to fit 3 eps per disc or 352x480 and 2900kbps to fit 4 eps per disc (a bit over 3 hours).

I've even gone as low as 2350kbps with 256kbps AC3 to fit (5) 48 minute episodes onto a single DVD. But for that I didn't care much about the video quality (was a really crappy VHS tape to start, in LP mode).

(edit note: when I mention a rate like 2350, 3800, 6000, that's for the video stream only, audio stream would be added on top)

[Gazorgan]

When comparing an MPEG4 AVI bitrate to an MPEG2 bitrate, I make certain assumptions.

1) No Audio. Drop the audio out of the comparison. AC3 is AC3, and it's not really going to change between them. MP2 isn't as 'efficient' as MP3, but the difference is marginal when looking at the size of a DVD.

2) Resolution is relatively the same. I say relative because a 640x480 AVi is the same as a 720x480 MPEG (remember TV pixels aren't square, the ratio difference is 720/640....imagine that?).

Now having said that, a high quallity MPEG4 is roughly 1/2 to 1/3 the size of the same high quality MPEG2. This equates roughly to a 3 CDR AVI. Again I say roughly, you have to factor in length of movie and how much action there is. A lot of 90 minute movies can fit on 2 CDR's. Some 3+ hour movies need 4 CDR's.

A 2 hour AVI that's 3 CDR's long has a total bitrate around 2350. Drop out typical audio and you are around 2000. Using my rule of thumb, that's an average MPEG rate around 4000-6000. Throw in a peak around 8000 and you are right in the ballpark.

Again, these are generalizations, based on years of personal experience. it's also based on being artifact free. It also explains why 1 CDR AVI's tend to be 320x240.