CBR w/Maximum Bitrate = Dissapointing

[jcm0320]

I decided to use 8.5gb Dual Layer DVDs so that I could use the maximum bitrate. These things are really expensive ($2+ a peice).

So I took 2 1/2 hours of video and encoded it at CBR 8000 Kb/s. The result is a video that doesn't look as good as when I used 4.7gb DVDs with a VBR setting of 2000/4000/8000.

When I use CBR and max. bitrate, the video file looks a little "messy." It's kind of hard to describe. A few artifacts show up a lot more, especially around objects. If someone is relatively still, it's like they have a little bit of distortion surrounding their entire body. I suppose it's possible that too much bitrate can be used? It seems like it. Or maybe VBR 2-pass just provides a better picture than CBR.

When I use VBR with the settings I mentioned above, the picture comes out looking pretty close to what it actually looked like when I recorded it off of TV. But the reason why I still chose to buy 8.5gb DL DVDs is because the material I have is priceless and I wanted to preserve it as best as possible. Unfortunately it seems like the $20 DVDs (10 pack) were worthless.

It's a shame, too, because I thought that being able to use the max bitrate would solve everything.

Can anyone else here relate to what I am saying? It does seem like I can recall at least one person saying they also prefer VBR over CBR. But I just don't understand why it has to be like this. It seems logic would be that maximum bitrate with CBR would work perfectly.

[j4gg3rr]

What encoder and settings are you using?

[guns1inger]

The maximum you can use is actually 9800 kbps for video. I regularly use 9200 - 9400 as a maximum for VBR encoding. However I suspect something else must be at play here.

As was asked, what encoder are you using ? Also, what is the source, and how do you acquire it ?

[jagabo]

In all likelihood you deinterlaced, resized interlaced video incorrectly, or you have the wrong field order.

[Cornucopia]

If your were going to go to all the trouble to get $2 DL discs, you could have at least have encoded something higher than 8kbps! That isn't the maximum available, you know. If you made a comparison of CBR vs. VBR, with 8kbps as average for both, at certain times the VBR rate will go higher --WHEN IT REALLY NEEDS IT. Not true with the CBR.

Maybe your material needs it...

Or maybe you could use a little help understanding how to best encode...

Scott

[dphirschler]

Decide what bitrate you need for audio. I would suggest AC3 224 kbps. That will leave you with 9570 bitrate left. So set that as your max. Then check out a bitrate calc such as https://www.videohelp.com/calc.htm to determin your avg bitrate. I got 3837 as your average bitrate. Your min should be 0, not 2000. By not using 0, you are wasting precious bitrate.

Still 3837 seems pretty low to me. For precious footage, I'd consider splitting it up to two discs or using the dual layer DVDs with VBR. Using the bitrate calc, I got 7178 for an avg bitrate using the DVD9 (7.95GB) setting. That sounds just about perfect.


Darryl

[Wile_E]

https://www.videohelp.com/dvd
Scroll down to "Technical Info for DVD-Video".
"Total bitrate including video, audio and subs can be max 10.08 Mbps (10080 kbps) "

So you can set the max to 9800kbps video with 256kbps audio = 10080kbps.

[dphirschler]

https://www.videohelp.com/dvd
Scroll down to "Technical Info for DVD-Video".
"Total bitrate including video, audio and subs can be max 10.08 Mbps (10080 kbps) "

So you can set the max to 9800kbps video with 256kbps audio = 10080kbps.

Interesting. I wonder why the discrepancy? Is the Videohelp Bitrate Calc not correct, or is there something we are missing in our understanding?


Darryl

[redwudz]

Many players can handle bitrates up to 15,000kb/s, the 10,080kb/s combined bitrate is a 'suggested' maximum, not part of the DVD specification, AFAIK. I try to stay in the 8500 - 9500kb/s range for maximum quality as all players are supposed to handle that.

[edDV]

I want to understand the capture and what kind of TV source. If it were a HD capture (high quality) downsized to 720x480 and then recorded full bitrate then it should have looked very good indeed.

[jcm0320]

Sorry, I should have added a lot more information to my original post.


Encoder: TMPGEnc Express 4.0

Settings:

Video System: NTSC
Encode Mode: Prioritize Quality
Aspect Ratio: 4:3 Specs
Rate Control Mode: CBR (Constant Bitrate)
Audio Format: Dolby Digital, 224 Kb/s
Video Size: 720x480 Locked
Average Bitrate: 8000 Kb/s
DC Component Precision: 10 bit
Motion Precision Search: Highest (with error correction)

Source: Cable Television (using Panasonic AG-1980 as a tuner)

*The program itself was broadcast via the Fox 8 studios in Cleveland.

Capturing Device: Canopus ADVC 110

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The reason why I chose 8000 Kb/s is because I thought it was the most safe bitrate to use. I've gone around 9200 Kb/s before and the audio was sputtering in my DVD player. That may have been because I was using Mpeg-1 Audio Layer II at the time. Perhaps using that audio format required more "power" from the DVD player? I don't know.

Anyways... Since then I've tried to stay at 8000 Kb/s just to be on the safe side. I've also chosen to use Dolby Digital audio since it appears to be a standard. Although I have never tested going above 9000+ Kb/s while using DD audio.

----------

In regards to interlaced/deinterlaced and field order...

When I import the video into TMPGEnc Express 4.0, this is what it says:

Display Mode: Interlace
Field Order: Bottom Field First
Aspect Ratio: Pixel 10:11 (4:3)
Framerate: 29.97 fps

I assumed that TMPG automatically detected these specs in the video file itself.

I did find one thing to be strange though...

After converting the file to mpeg 2 using the settings from above, I opened the video in TMPGEnc DVD Author 3 and this is what that program said...

Display Mode: Interlace
Field Order: Top Field First
Aspect Ratio: Pixel 10:11 (4:3)
Framrate: 29.97 fps (greyed out)

*Notice how after converting the video file to mpeg2 via TMPGExpress, the field order for the mpeg2 is now "Top Field First" unlike the original AVI file which was "Bottom Field First."

Is this normal? Or would it suggest that I accidently changed the Field Order in TMPGExpress?

(Which I swear I did not do by the way, because I have noticed it does this for every video I encode.)

Or are these settings not "detected automatically" and instead are meant for me to change them myself.

[jagabo]

TMPGEnc Plus often gets the source field order wrong. I assume Express is the same. But in this case it got the field order right, BFF (from the ADVC 110).

Field order is easily reversed by shifting the frame up or down by one scan line. TMPGEnc Plus is smart enough to do this if you give it a BFF video and request TFF output. I assume Express is the same. TFF is more common on DVD so maybe Exress does this automatically.

Try using GSpot to verify the field order of your MPEG file. As noted above, TMPGEnc is often wrong. You can also use DGIndex if you have DGTools (for AVISynth) installed.

The symptom of encoding with the wrong field order is very jerky video whenever theres is motion. 30 jerks every second with fully interlaced NTSC, fewer with telecined film. This doesn't sound like what you are seeing.

It might help if you posted a sample of the output video or even just a frame grab so everyone can see what your artifacts are. 8000 kbps CBR should give decent results, certainly better than 2000<4000<8000 VBR.

[jcm0320]

Gspot says the source video is "BFF".

It says the mpeg2 file is "TFF".

[jagabo]

You can verify that the MPEG file is correctly encoded by using a simple AviSynth script:

DirectShowSource("filename.mpg")
AssumeTFF()
Bob()

Open that with an editor that will let you single step through frames (VirtualDub for example) and watch the motion. If it jerks back and forth the video is encoded as TFF but contains BFF frames.

What did GSpot say about the bitrate of your MPEG file?

[edDV]

I haven't used TMPGEnc Express in a while. Normally I set the MPeg2 encoder to BFF for DV input. If field order is reversed, you will see jumpy motion. It will look like two steps forward one back with pans and slow movement.

TV video can be full interlace (like live events or sports) or telecined for film. Film encoding will look much better if you IVTC first.

Professionally shot video should be smooth enough for VBR to help at 8000kb/s average. Shaky hand held home video may do better with CBR at higher bit rates.