Minimum Video Bitrate

[edekba]

Hey guys i was wondering what is the general rule of thumb about bitrate. How low is too low so that I need to increase the target size from say 1cd to 2cd or 1/5DVDR?

Im using x264 Xbox High Res Profile, but i'm just curious to what is the rule of thumb? Is 700kbps good enough?

[bond]

i dont know any rule of thumb because the needed bitrate is heavily dependent on the video to be encoded

either way i would guess that 700 is not enough for 1080p, but i am just guessing so try it yourself

[edekba]

yeah i thought as much. Im only encoding DVDs at 640x480 or 640x352, so hopefully it's enough. I was asking because it takes about 7 hours per movie for me to encode using x264. But thanks

[PuzZLeR]

Hi,

I was interested in this question from a compliance point of view, not quality.

Sure encoding at 700kbps should look weak in quality with 1080p, even with AVC and you should use more, but that's not the question I have.

In fact, what would be the allowable minimum, such as in BD or HD-DvD standards? I know they have a maximum of 48,000kbps, but do they have a minimum as well? There's no info on this anywhere.

(Someone told me they think it's 5000kbps. Is that high a bitrate really the minimum, even for AVC?)

[neuron2]

How low is too low 0 bits per second is definitely too low.

[foxyshadis]

I've done some anime at 6fps, 20kbps, though. It's blocky but at least as watchable as those age-old realvideo clips. =p

I don't believe there is a minimum for DVD, since I've tried making one at constant max quantizer (31?), I-frame every 15 frames, and it worked, so I imagine that whatever you get from q51 in avc is still high enough.

[PuzZLeR]

I don't believe there is a minimum for DVD, since I've tried making one at constant max quantizer (31?), I-frame every 15 frames, and it worked...

You know what? I gotta try that. :cool:

[xyloy]

Hi,

Hi,
In fact, what would be the allowable minimum, such as in BD or HD-DvD standards? I know they have a maximum of 48,000kbps, but do they have a minimum as well? There's no info on this anywhere.

There is a limit of video resolution/frames per second/Kilobits per second due to the maximum data the processing unit(*) can manage at the same time before the playback begins to slow down.

(*)most of the time, the CPU. But on a low-end PC a good videocard can help a lot! It's very impressive: an old Intel Pentium 3 450 MHz CPU with a Radeon 8500 videocard can play a Video DVD(or even a XviD video with QPEL and/or GMC in it) whereas the same CPU with an old 3dfx Voodoo 3 2000 cannot. And there's no GPU decoding involved, although the 8500 can process the iDCT for MPEG-2, has much more 2D/3D capabilities(enabling the use of VMR7/VMR9(renderless or windowed) output), and accepts much more colorspaces, including YV12.

But there's no limit to compression(lowering the bitrate), except the maximum quantizer. Of course, in the quality department, the house is on fire at 1 kbps. :D
(Note that I've never seen an encoder reach 1 kbps or even near)

(oh god! another post two hours after midnight! The Gremlins are coming for me! :p )

[Sergey A. Sablin]

But there's no limit to compression(lowering the bitrate), except the maximum quantizer. Of course, in the quality department, the house is on fire at 1 kbps. :D
(Note that I've never seen an encoder reach 1 kbps or even near)

(oh god! another post two hours after midnight! The Gremlins are coming for me! :p )

resize video to 1 macroblock, convert it to 1 fps and you'll have much less than 1kbps ;)

[PuzZLeR]

Thanks for the feedback guys.

An eventual goal of what I'm encoding now in H.264 is, hopefully, for BD and/or HD-DvD playback in the future. Even though H.264 is a standard on these devices, I may still need to re-encode/transcode these clips somewhat.

But, the reason I asked about minimum allowable bitrate is because I'm wondering if I can keep the lower bitrates that I currently have for these clips.

For example, if I have an H.264 clip encoded at 2000 kbps, and the min bitrate for BD is, for example, 5000 kbps (even with H.264), then I may as well keep it in its original MPEG-2 form and quality, and encode it later when the time comes, since I will have to bump up the bitrate anyway.

My real question is that: Does anybody know if it's possible to have video on these next-gen formats in these lower bitrates of 1500-2000 kbps in H.264 format? On a 50GB disc you're looking at 50-75 hours of playback video. This would be great for a bunch of SD clips like Tv programs/documentaries or even over 1000 music videos, all on one disc, which would be truly impressive.

(I'm talking video playback, like a DvD, not data on a disc and they play like DivX or mp3.)

[Sergey A. Sablin]

My real question is that: Does anybody know if it's possible to have video on these next-gen formats in these lower bitrates of 1500-2000 kbps in H.264 format? On a 50GB disc you're looking at 50-75 hours of playback video. This would be great for a bunch of SD clips like Tv programs/documentaries or even over 1000 music videos, all on one disc, which would be truly impressive.

(I'm talking video playback, like a DvD, not data on a disc and they play like DivX or mp3.)

actually I don't see any reason to refuse playback of low bitrate video if every format specific options were set correctly.
Use profiles, levels, other specific features of BluRay and HDDVD formats and hope that authoring application will mux it correctly. If you'll be able to do this, then everything shall work.

If you're targeting playback of your thousand movies on PC, than why do you care about formats etc? if you're targeting hw players - see above.

[PuzZLeR]

True enough SAS. I agree. Bitrates lower than 2000 kbps for MPEG-2 would be acceptable for DvD and SD material. Since BD/HD-DvD accepts SD material, and a better compression format like H.264, I don't see why it can't accept lower bitrate video of 1500-2000 kbps either.

Higher quality per smaller file size + a much bigger disc size = tons more fun per disc. Looking forward to it. :)

And as far as "only PC playback" is concerned, life would be too easy.:rolleyes: If I only cared for PC playability of my video I may have never joined this forum in the first place. :p

[Jay Bee]

HD-DVD has minimum of 2500 kbps according to this post (http://forum.doom9.org/showpost.php?p=928478&postcount=94).

On the topic of SD on HD-DVD/BD, what I'd really like to know is whether 720 x 576 with a pixel aspect ratio of 16:15 is allowed or not (this results in a true 1.33 aspect ratio). Scenarist only accepts 12:11 which means a final aspect ratio of 1.36.

Last time I asked I got no responses. Are the official specs secret?

[PuzZLeR]

HD-DVD has minimum of 2500 kbps according to this post.

I would understand if this is a bare minimum for MPEG-2 at HD levels. I can't see this being a minimum for SD material in AVC format, in which 2500 kbps would be unnecessarily high for most clips. But at least it's not that much over 2000 kbps.

The best info I found on this is here:

http://www.videohelp.com/hd

Although, it doesn't get into too much detail and doesn't discuss min bitrate or PAR or any of that.