622 MPEG4 HD Recording Time

[Tom Bombadil]

I tried this a couple of weeks ago with no response.

Just wondering if anyone had a chance yet to record some true MPEG4 channels to see if you could get more hours of recording time out of it than the 25 hours of estimated recording time for HD MPEG2 content.

One might have to have a clean 622 and record only true MPEG4 content to see if they could put more than 25 hours on it before it fills up.

If Dish is achieving any compression efficiencies with MPEG4 (which is still an unknown at this time), then it should record 30-35 hours before it fills. Although Dish could have "hard-wired" their recording timer so that it would say the disc was full after 25 hours, even if it wasn't.

I know with my 7100 and 510 DVRs that I could get more hours of recording off of the lower bandwidth channels than those that had higher bandwidth, so the Dish built-in timers were not always (well, never) correct about how much time was remaining.

 

[jrfuda]

Here's a "cut'n paste" of a post I made in another thread:

...Empty, the 622 says 30 hours HD and 200 houes SD.

I recorded 90 minutes of HD and had 28 hours 38 minutes of HD remaining.

I should have used 5% of my total capacity, but only used 4.55%. Over time, that may net me 2 hours 42 minutes of extra time.

Then again, it was SNL I recorded (from OTA), and it probably was low bitrate. If it were an action movie or something with lots of movement, it might have used 1 hours 45 minutes of space for 90 minutes of HD.

I bet, though, that the bitrate is higher on the OTA broacasts than it is on the Sat HD channels, so we likely still have a bit more than 30 hours worth of HD available.

It's always better to promise less and deliver more.

I've been reading a bit about mpeg4 and satellite brodacasting lately.

There seems to be 2 camps.

-1 Use mpeg4 so you can broadcast at the same quality at a lower bitrate

-2 Use mpeg4 so you can broadcast at higher quality at the same bitrate.

If Dish subscribes to camp 1, our recording times will go up after the conversion

If Dish subscribes to camp 2, our recording times will not change after the conversion

If Dish goes camp 1, they'll probably change the "time remaining" estimates with a software upgrade after they're boradcasting 100% mpeg4.

my guess, anyway.

 

[David_Levin]

I think you missed option 3. Dish is scaling 1920x1080 locals down to 1280x1080.

So, dish is Using mpeg 4 AND downrezzing to a lower quality and even lower bitate in a misguided attempt to try and keep up with cable and DirecTV.

On the plus side it should give us more recording time. Not sure if they will do anyting with the "time remainig". The problem is that there are just too many channels using too many different bit rates. Historically, premiums like HBO get more bits then locals, so the time remaining has always been an estimate.

The (Comcast) Morotola box just tells you the % of HDD remaining.

 

[ronjohn]

I recorded the local Atlanta HD version of 24 today. I paid attention to the time remaining displayed. After one hour of 24, the time remaining had dropped 35 minutes.

 

[Tom Bombadil]

Well, now that's something. At least a bit of info.

All of our 622 owners, except for ronjohn, that are receiving HD LiLs are holding out on us.

As to 1280x1080 channels, if the bitrates remain high, then recording times should also be about the same as true HD.

 

[David_Levin]

As to 1280x1080 channels, if the bitrates remain high, then recording times should also be about the same as true HD.

Well, that's absolutely true, but the whole point of lowering the resolution is to lower the bit rate.

That's how they are packing 4 HD LIL channels onto an LNB. Charlie has admitted that the improvement due to mpeg4 is way less the expected. The real-time encoders just aren't there yet.

 

[ronjohn]

I will delete the entire 2hours 4 minutes tonight after my wife is able to watch it, and let you know how much the available time estimate rises.

 

[jrfuda]

Check out this site for how much potential mpeg4 has if they can ever get the most powerful version of the codec, mpeg4-10, to work in real time:

http://www.balooga.com/mpeg4.php3

Here's a exceprt explaining some of the current limitations:

The processor power required by the new MPEG4-10 algorithm is an order of magnitude greater than the older MPEG4-2 algorithm. Using a 2Ghz Pentium 4 with 768MB RAM, encoding an 8 second sequence using the Microsoft MPEG4-2 encoder took under 60 seconds. Encoding the same sequence using the reference MPEG4-10 encoder took two hours. Note that the reference MPEG4-10 encoder is a proof of concept and is not yet optimized.

However, if they get it to work:

We were hoping to fit upwards of 25 full screen video channels into a transponder by encoding each channel at an average of 1.2Mbps. All channels would be stat muxed within a transponder. Stat muxing channels allows an encoder to maintain video quality by varying the bit rate for that channel above or below the 1.2Mpbs average, as dictated by the source material.

I have no idea what satellite company this guy works for, but those are some amazing figures - both in the potential of mpeg4-10, and the limitations (in terms of processing requirements) of it ever being implemented for real-time use.

Wouldn't be too much of an issue for channels without live feeds (just convert everything to mpeg4-10 once, and store it) but would defineately limit live channels.

 

[navychop]

Thank you for the link. Those frames really speak volumes.

 

[The Big Wood]

I want to know if there is a difference in recording times, so I will try something tonight.

My test will be to record my local CBS broadcasted in MPEG 4 and also record the CBS from New York which is still in MPEG 2, both recording at the same time on the same show (preferably a 1 hour HD show). After recording, I will:

• Note the time left on the 622 before deleting either program
• Delete one of the programs
• Note the time left on the 622
• Delete the last program
• Note the time on the 622
• Figure out the amount of time each program requires by using simple math

This should give us a rough idea of the differences between MPEG 2 and MPEG 4 recording times. If Dish is squeezing the NY CBS to something like 1440x1080 but my local channel is broadcasted at a different size, then it won't be extremely accurate. I will be using WGCL Channel 46 from Atlanta for my local if anyone that has the capability of monitoring screen sizes and bitrates wants to keep tabs on it. I will be shooting for a 1 hour HD show after 9:00pm (I can't interfere with my wife's American Idol!). If there is a CSI show on tonight, I will probably try that show.

 

[dfergie]

NCIS and the Unit tonight...to try out on...

 

[dfergie]

I have 1:19 of 24 from my local and 0:03 minutes of Discovery HD and mine shows 29 Hrs 11 minutes of HD time left 194 hr 28 minutes of SD avail...

 

[The Big Wood]

Recording the new show "The Unit" on both CBS feeds right now. I would stay up, but Spring is blooming around here and I think I got some allergies kicking in. Shouldn't have rode home from work with my windows down the last couple of days!

Will update in the morning...

 

[The Big Wood]

Oh well, I stayed up after all. Here are my findings:

Based on the simultaneous recording of the show "The Unit" on CBS on 3/7/06 from my local MPEG4 channel (6366 WGCL Atlanta) and the MPEG2 channel (9483 CBS HD New York) for exactly 1 hour on the 622 receiver and shown as the amount of time taken up on the 622 hard drive:

MPEG 4 record time of 4.1 hours, or 4 hr 6 min.
MPEG 2 record time of 4.7 hours, or 4 hr 42 min.

This difference represents a 12.77% decrease of hard drive space when using MPEG 4 over MPEG 2.

This in turn translates to an estimated time of 34.39, or 34 hr 23 min, of recording time of MPEG 4 broadcasts. The 622 is estimated to hold 30 hours of MPEG 2 record time. A net result of nearly 4.5 hours extra record time with MPEG 4.

In summary, not a huge difference between the two formats right now (if screen sizes were the same and quality levels were the same between the two broadcasts at the time of this test). Maybe the encoders will give better results in the future for MPEG 4, but I will take whatever I can get!

Good night!

 

[dfergie]

Recorded Mpeg 2 Cold Case from TNT 1:04, 2 Joeys total time 1:04, According to Jims 1:34 have 24 1:19 and 0:03 of return to flight mpeg 2.. total time HD 26hrs 22 min... SD: 175hr 43 min avail...

 

[ronjohn]

My wife finally watched last weeks episode of 24. I deleted 2 hours 4 minutes or 124 minutes. The estimated time available changed 1 hour 13 minutes or 73 minutes. That is a factor of 1.7. If that holds for the entire recording time, then estimated 30hours would actually record approx. 51 hours.

 

[voripteth]

I thought it was reported that the MPeg4 channels were really just wrapped MPeg2 streams. Are they really doing MPeg4 compression now?

 

[Smith P.]

I thought it was reported that the MPeg4 channels were really just wrapped MPeg2 streams. Are they really doing MPeg4 compression now?

Your thought was wrong and you posted off-topic.

 

[The Big Wood]

I thought it was reported that the MPeg4 channels were really just wrapped MPeg2 streams. Are they really doing MPeg4 compression now?

Most HD locals (the only exceptions I am aware of are LA and NY) are transmitted as MPEG 4. The new Voom channels, UniversalHD, and ESPN2 are transmitted in MPEG2 with MPEG4 headers to fool the older HD receivers into not accepting them.

 

[Kirby Baker]

My wife finally watched last weeks episode of 24. I deleted 2 hours 4 minutes or 124 minutes. The estimated time available changed 1 hour 13 minutes or 73 minutes. That is a factor of 1.7. If that holds for the entire recording time, then estimated 30hours would actually record approx. 51 hours.

Not knowing the source of your 24, OTA or mpeg4 sat, there is another factor that could be coming into play here. I highly doubt the 622 is using any special formula for time calculation, and probably was set to baseline off a 1920x1080i channel. 24 is a 720p channel, so you already have quite a difference in size/time comparisons to a 1920x1080i channel. Probably would be best that everyone uses the same resolution channel for making comparisons, at least when comparing mPEG2 and MPEG4. Just a thought... Or am I on crack?