Two pass encode vs. single pass for sports DVD?

[blplhp]

Hi all,

Next week I will be creating a video file from my project file. I am making a sports DVD highlight movie of my son¡¦s soccer season (fast action video capturing, lots of panning and zoom). The project file also has many still shot photographs and will also include, slow motion segments, LTG, etc. I am planning on creating the video file using Terry Stetler¡¦s advice of custom GOP settings ( I-frames set to 6 instead of 15, and the horz. pel movement and vert. pel movement set to 16 instead of 0). The file will be about 1 hour long. My project file consists of DV-AVI video clips and I will render the file to the following create video settings:

MPEG files
24 bits, 720 x 480, 29.97 fps
Lower Field First
(DVD-NTSC), 4:3
Video data rate: Variable (Max. 8000 kbps)
Audio data rate: 256 kbps
Dolby Digital Audio, 48 KHz, 2/0(L,R)

Based on the above information, would I get even better video quality with a two pass encode or the default single pass encode? Or do I need to be the guinea pig on this one? I¡¦d rather not if someone already has the knowledge and/or experience with this. Thanks.

[Trevor Andrew]

Hi

As your video is approximately 60 minutes, you will be able to use Constant bit rate.
That means that all the video will be coded at 8000kbps. The average being 8000 kbps

If you use Variable bit rate then a proportion will be coded at 8000 kbps.
Some encoded at 7500 some lower, the average being lower than 8000 kbps.

Use Constant bit rate. Quicker to re-code and you get top quality.

As for your advice on custom Gop settings, I have no idea. But are these settings related to Variable only, or associated with Constant rate?

Interested


Regards Trevor

[GeorgeW]

As for your advice on custom Gop settings, I have no idea. But are these settings related to Variable only, or associated with Constant rate?

The settings are not specific to VBR (i.e. you can use them for either VBR or CBR).

I remember reading someone had some issues with enabling the ADVANCED button in either VideoStudio and/or MovieFactory (i.e. the encoder did not properly use their custom settings). I don't remember where I saw that though

But given the high bitrate that can be used, I'd say there's really no need to make any custom settings -- just encode as usual (I'd even recommend dropping the video bitrate down to ~7500kbps CBR -- to make a more compatible disc if it's going to be distributed to team players/parents/coaches...)

Regards,
George

[blplhp]

Thanks, Trevor,

After reading your response, I re-read Terry Stetler's tutorial on this issue and he mentions using Constant Bit rate for action mpeg files, therefore rendering my question about the two pass encoding a moot point, since two pass encoding is greyed out when selecting Constant Bit Rate. I will create the video file both ways.....8000 CBR with the GOP and hor/vert pel movement adjustments and 8000 CBR without the custom changes and see which looks better on my soccer DVD.

Terry recommends using VBR for slideshows and video mpegs where there is not much in the way of motion changes. Use CBR for action type mpegs, where there is alot of camera movement.

What spurred my query was a recent post by dmz entitled Two Pass Encode and it just tweaked my brain about this issue and so I jumped the gun a little and started a new thread. Sorry for the additional thread on this issue, but hopefully someone else can learn from this discussion.

[2Dogs]

Hi Brian,

if you have the time to spare, you might try variable bitrate. You could do tests on a small section of your project that features a lot of movement.

Whilst I would agree that using constant bitrate is more straightforward, and it will be quicker to encode, I think that you might possibly squeeze a little more picture quality out of your project if you use variable bitrate.

Since you're using a compressed audio format, you can raise the maximum bitrate up to 9800 kbps, though most commercial DVD movies use 9500 kbps - though they usually have additional audio streams. (the DVD standard sets a limit on the combined audio and video bitrate)

Assuming your source material is good, it's possible that you could get slightly improved picture quality - but the only way to confirm this would be to do your own tests. Then you can judge for yourself whether it's worth the approximately doubled rendering time for using two-pass variable bitrate. I use it if I'm going to make multiple copies of a disc to give out.

Since you have a significant amount of slide-show footage, you'll probably find that for your one hour project, even using the maximum allowable variable bitrate, your project might render to less than 4.35GB.

good luck!