JVC DR-M10 FR Mode

[qlizard]

I've got some old home camcorder recorded football tapes where I want to preserve as much quality as possible. I've been recording all my other home movies in XP mode. But these games are about 75 minutes long and would take two disks in XP mode. If go to FR75, does the bitrate just go down a little, or does it drop down to SP level? And if I decide to use two disks, should I use FR40 for each disk to even get more quality? I guess what I'm asking is whether the bitrate adjusts dynamically depending on what FR number you choose.

Also if you use FR mode, do the different bitrates cause problems if you decide to reauthor the disks?

thanks

[midnightsun]

FR75 means that approximatively 75 minutes will fill up the disc. SP is 120 so no, it doesn't drop to SP level. (bitrate for FR75 will be about 60/75=0.8 that of XP)

FR40 doesn't exist because if you filled up a disc with 40 minutes of footage you'd be way outside DVD specs as far as max bitrate is concerned. XP gives you the highest bitrate you can record at.

[Coruscant]

If you go by bitrate, XP w/PCM isn't the best. The video bitrate assigned to it is barely higher than that for FR140. The highest bitrates reached by the JVC M10s as identified by by my editing software are reached at FR110 where you get a maximum of 9000 Mbps for video and 384 kbps for audio. Step down to FR115 and you keep that video bitrate and but audio drops to 256 kbps.

As for authoring issues, I've never had a problem with different bitrated programs on a single disc.

[FulciLives]

If you go by bitrate, XP w/PCM isn't the best. The video bitrate assigned to it is barely higher than that for FR140. The highest bitrates reached by the JVC M10s as identified by by my editing software are reached at FR110 where you get a maximum of 9000 Mbps for video and 384 kbps for audio. Step down to FR115 and you keep that video bitrate and but audio drops to 256 kbps.

As for authoring issues, I've never had a problem with different bitrated programs on a single disc.

At 110 minutes with 384kbps audio the video bitrate MAY peak at 9000kbps but the AVERAGE video bitrate will be MUCH lower ... probably somewhere around 5500kbps.

Also 256kbps AC-3 is more than enough for standard 2 channel mono/stereo/dolby pro-logic surround.

- John "FulciLives" Coleman

[Coruscant]

At 110 minutes with 384kbps audio the video bitrate MAY peak at 9000kbps but the AVERAGE video bitrate will be MUCH lower ... probably somewhere around 5500kbps.

Also 256kbps AC-3 is more than enough for standard 2 channel mono/stereo/dolby pro-logic surround.

Once I noticed that, I stopped recording at any speed faster than FR115.

[qlizard]

If you go by bitrate, XP w/PCM isn't the best.

But XP w/ AC-3 is the best, correct?

[Coruscant]

But XP w/ AC-3 is the best, correct?

While XP w/AC-3 may well be better picture wise than XP w/PCM, it wouldn't be better sound wise since AC-3 is compressed audio and PCM isn't. But given the sources I'm guessing most of us use, I doubt PCM is of any value. I used it once and couldn't tell the difference.

Perhaps because XP (aka FR60) w/AC-3 doesn't require as much space for its audio as XP w/PCM, its maximum video bitrate may well be higher, 9000 Mbps instead of 7680. If so, then it wouldn't be any better than FR110.

[qlizard]

Referring back to FulciLives' comments, does the 9000 Mbps at FR110 represent the average bitrate or peak?

Comparing apples to apples, you would have to think XP mode (FR60) w/ AC-3 assigns a higher avg bitrate to the video than FR110 w/ AC-3 and therefore the video quality overall would be somewhat better.

[FulciLives]

Referring back to FulciLives' comments, does the 9000 Mbps at FR110 represent the average bitrate or peak?

Comparing apples to apples, you would have to think XP mode (FR60) w/ AC-3 assigns a higher avg bitrate to the video than FR110 w/ AC-3 and therefore the video quality overall would be somewhat better.

I'm not trying to be rude but me thinks that Coruscant is a bit clueless here ... as in bitrate clueless.

The upper limit of the video bitrate must be restricted when using LPCM WAV audio in a way that is more restricted than when using AC-3 audio.

Therefore when using AC-3 audio the video bitrate should peak higher. Since the XP (1 hour mode) is the only mode that uses LPCM WAV audio I don't see this being an issue.

One should really be thinking here in terms of AVERAGE video bitrate. It seems that Coruscant is stuck more on MAXIMUM video bitrate than the AVERAGE video bitrate.

That of course is a wrong way of thinking about it as it is the AVERAGE bitrate that determines the overall compression (and therefore compression "quality") and not the MAXIMUM.

For instance let us say you record something twice and each time you use an AVERAGE video bitrate of 5000kbps but with one recording you use a MAX of 9000kbps and in another another recording you use a MAX of 7500kbps.

Now the one with a MAX of 9000kbps might look better but only when it comes to those very hard-to-encode moments. Even then the difference between 7500kbps as a MAX and 9000kbps as a MAX is not that significant.

Example two:

You record a program once at an AVERAGE of 6500kbps with a MAX of 9000kbps and then again at an AVERAGE of 4000kbps with a MAX of 9000kbps.

The one with the higher AVERAGE is the one that will overall look superior.

I hope this helps.

[FulciLives]

Referring back to FulciLives' comments, does the 9000 Mbps at FR110 represent the average bitrate or peak?

If you use an AVERAGE video bitrate of 9000kbps then you MUST use AC-3 or MP2 audio and even then you would just barely be able to fit 60 minutes per disc. So obviously the math doesn't work ... no way you can have an AVERAGE video bitrate of 9000kbps and fit 110 minutes.

Comparing apples to apples, you would have to think XP mode (FR60) w/ AC-3 assigns a higher avg bitrate to the video than FR110 w/ AC-3 and therefore the video quality overall would be somewhat better.

60 minute mode with LPCM WAV audio MUST use a lower video MAX bitrate than a 60 minute mode using AC-3 audio. That is becaue AC-3 audio hits the MAX bitrate at 448kbps whereas LPCM WAV audio has a fixed bitrate of 1536kbps. Since LPCM has a highter bitrate it takes up more space ... plus a DVD can only handle so much BITRATE at once.

I doubt though that you will see that big of a difference unless the footage is extremely hard-to-encode. Home made camcorder stuff would fall into that category since the image tends to be very shaky and moving all the time. That would be hard to encode.

So for video ... even at the 1 hour or 60 minute mode ... you might be better off using AC-3 audio instead of LPCM audio.

But this nonsense that FR110 is better than any of the modes (with a shorter running time) is nonsense ... especially once you take the 1 hour / 60 minute mode out of the mix.

In short (as an example) ... FR70 will always look better than FR110

FR90 will always look better than FR100

FR110 will always look better than FR115 or FR130

etc. etc.

- John "FulciLives" Coleman

[midnightsun]

Referring back to FulciLives' comments, does the 9000 Mbps at FR110 represent the average bitrate or peak?

Comparing apples to apples, you would have to think XP mode (FR60) w/ AC-3 assigns a higher avg bitrate to the video than FR110 w/ AC-3 and therefore the video quality overall would be somewhat better.

I'm not trying to be rude but me thinks that Coruscant is a bit clueless here ... as in bitrate clueless.

yes basically that is the point.

What Coruscant sees as "higher bitrate at FR110" is merely the peak bitrate value the recorder stores in the mpeg header of the file it creates. Average bitrate is another story.

As pointed out, at 110minutes/disc the average bitrate is just over 5000kb/s (around 5200 using 384kb/s ac3 audio). XP has an average bitrate of 8820kb/s using the JVC.

[qlizard]

From those who have experience with this particular recorder (or I guess the M100) using grainy fast action VHS home movies as the source, where do you think the "sweet spot" is? In other words, do you see a difference between XP mode and FR65, 70, 75?

I understand its totally subjective and depends on the particular source but I just want to get an idea of what setting other people are using. Again, I want to preserve as much quality as possible but wouldn't mind getting 15 minutes more in there.