Intersting Digital/Analog Observation.

[TexasGrillChef]

Last night my TiVo HD (bedroom unit) recorded "The Alaskan Experiment" at the same time on both tuners.

One tuner was on the ANALOG Discovery Channel, The other tuner was on the DIGITAL Discovery Channel.

The Alaskan Experiment showed on both channels at the same exact time. Same "Broadcast" as all Commercials & both shows were in "Sync" with each other at the time of the recording.

Yes, I programmed the TiVo HD to record both channels intentionally.

Here is the interesting observation.

The ANALOG version of the show, exactly 60 min long was recorded at "BEST" quality and is 2.69gb in size.

The DIGITAL version of teh show, exactly 60 min long, was also recorded at "BEST" quality and is ONLY 1.69gb in size.

I then viewed both shows on my 32" LCD HDTV, hooked via HDMI, TiVo HD outputting at a FIXED 1080i. (The prefered input resolution for my TV).

I compared both shows. The Analog show had NO DD5.1, the Digital version had DD5.1. The Digital show LOOKED much better then the analog version.

So even though the file size of the Analog verion was 1gb larger, It didn't have DD5.1 & the picture quality was still NOT anywhere near as good!

I have come to the conclusion. Don't record analog stations unless you have too.

BTW, FYI... Neither the Analog station nor the digital station was "Copy Protected" (0x02). Yet on my Living room S3 (Oled display unit). It recorded the same show on the digital channel of Discovery & The show had copy protection enabled. Weird.

TGC

Ack! I just caught my typo in the Title line! Can't Change it :(

[dnorth12]

"Intersting" - kinda like oil and erl - in Texas speak ain't it?

Thanks for this post - I kind of always wondered about some of the things you noticed.

Did you happen to notice any hiccups in the digital broadcast that were or weren't there in the analog, like pixels, split second jumps ahead? I kind of think that some of the things that get reported about the S3 and pixel problems aren't necessarily an S3 issue and more a broadcast issue, but you won't know that unless you have two of the same to compare to like you did.

[TexasGrillChef]

"Intersting" - kinda like oil and erl - in Texas speak ain't it?

Thanks for this post - I kind of always wondered about some of the things you noticed.

Did you happen to notice any hiccups in the digital broadcast that were or weren't there in the analog, like pixels, split second jumps ahead? I kind of think that some of the things that get reported about the S3 and pixel problems aren't necessarily an S3 issue and more a broadcast issue, but you won't know that unless you have two of the same to compare to like you did.

Nope no lost pixels, skips, jumps, artifacts, blips, or anything else that would otherwise degrade the signal, the sound, the picture or any other aspect of quality. Neither broadcast had any problem.

TGC

[moyekj]

The recording quality specification has no effect on Digital recordings - those are recorded as broadcast.
Kind of surprising that you get both analog and digital SD versions of the same channel. For most digital simulcast implementations I've seen the cable channel numbers are identical and depending on equipment used to tune the channel map is set to map to either the analog or digital version. Under your system sounds like they have physically different channel numbers for both analog and digital versions - makes for a much longer channel lineup with a bunch of duplicates which makes you wonder why the heck it would be done that way??

For my headend, unless I pull out CableCards I can't get the analog version of any of the channels since the CableCard channel maps point to the digital versions.

[TexasGrillChef]

The recording quality specification has no effect on Digital recordings - those are recorded as broadcast.
Kind of surprising that you get both analog and digital SD versions of the same channel. For most digital simulcast implementations I've seen the cable channel numbers are identical and depending on equipment used to tune the channel map is set to map to either the analog or digital version. Under your system sounds like they have physically different channel numbers for both analog and digital versions - makes for a much longer channel lineup with a bunch of duplicates which makes you wonder why the heck it would be done that way??

For my headend, unless I pull out CableCards I can't get the analog version of any of the channels since the CableCard channel maps point to the digital versions.

I think they might do it this way, because in our market they advirtise as having over 350 cable channels. If you count the 3 duplicates for each of the network stations (Example FOX, Analog 4, Digital 358, HD 357), plus the 50+ analog channels (2-99) that also have digital duplicates such as discover (analog 3, digital 202, HD 256) Then our cable system has over 350 channels that we get. Oh and in Dallas we have about the 7 big locals & an additional 7 independants. the 7 Big locals have 3 channels (Analog, Digital & HD). The 7 local independants have 2 (Analog, Digital).

The 7 big networks in our area are... Fox, CBS, NBC, ABC, CW, PBS, Univision). (Univision is the big spanish network)

I just thought it was interesting that the Analog recording had a file size almost twice the size of the digital broadcast one. 2.9gb compared to 1.9.

TGC

[mattack]

The ANALOG version of the show, exactly 60 min long was recorded at "BEST" quality and is 2.69gb in size.

Though how big would it have been in Tivo Basic? (yes, I record in basic on my TivoHD & S3.. When I get an antenna some eon then I will try to get OTA digital, and I would record more QAM channels if cable cards were not required... Yes, I am not using the S3 & HD to their fullest extent. I got them *because* of the lifetime transfer offers.)

[moyekj]

I just thought it was interesting that the Analog recording had a file size almost twice the size of the digital broadcast one. 2.9gb compared to 1.9. Perhaps the Tivo encoding of analog channels is CBR (constant bit rate) instead of VBR (variable bit rate), so consumes a lot more space than a normal VBR encoding. Probably easy to find that out with VRD or some other mpeg2 editor.

[msdonnelly]

If you had an option for "Best" quality, you weren't recording a digital signal since, as was pointed out earlier, digital is recorded as is. Did the "Best" for the digital channel just slip out of your fingers unintentionally?

[TexasGrillChef]

Though how big would it have been in Tivo Basic? (yes, I record in basic on my TivoHD & S3.. When I get an antenna some eon then I will try to get OTA digital, and I would record more QAM channels if cable cards were not required... Yes, I am not using the S3 & HD to their fullest extent. I got them *because* of the lifetime transfer offers.)

Not fure sure.... but the quality of "BEST" still didn't even come close to its "DIGITAL" equivilent. So "BASIC" I am sure would be even worse.

TGC

[TexasGrillChef]

Perhaps the Tivo encoding of analog channels is CBR (constant bit rate) instead of VBR (variable bit rate), so consumes a lot more space than a normal VBR encoding. Probably easy to find that out with VRD or some other mpeg2 editor.

I pulled both of my TiVo using TiVo Desktop. "Decoded" to MPG2. Loaded into ULead Videostudio 11 Plus and looked at their properties.

The Digital channel one, with the file size of 1.9gb did in fact of VBR encoding while the Analog did have Constant bit rate.

According to Ulead... the digital version had a compression ratio of 75% set. The Analog MP2 file had a compression ratio of 95%

TGC

[TexasGrillChef]

If you had an option for "Best" quality, you weren't recording a digital signal since, as was pointed out earlier, digital is recorded as is. Did the "Best" for the digital channel just slip out of your fingers unintentionally?

Probably! LOL good catch & yes I realize that now that I think about it. In a post I just posted a few minutes ago... (Above)

Ulead did notice a MPG2 compression factor on the Analog channel version of 95% and on the digital version of 75%.

I am assuming then that since the TiVo had to do a Analog to Digital conversion that at best quality it only compressed 5% of the conversion.

The digital channel version I am sure was compressed by TWC &/or Discovery channel and was compressed to 75%. But however was a pure digital signal using better ADC's then are built into the TiVo.

TGC

[blacknoi]

Ok, I always, ALWAYS get better black color depth on the analog versions of channels.

So much so that if <gasp> I'm watching a live SD channel, I'll flip over to my tv's internal tuner so I can watch the analog broadcast.

In my experience, a properly tuned / correct signal levels version of a SD channel always looks better than its compressed digital SD counterpart. You can bet on it.

Often times people confuse poor signal levels that analog broadcasts show snow as a result, as "worse quality" than the digital SD version. This is because the SD either works or it doesnt or is pixelated. What you don't realize is just how compressed that SD digital channel is. Your own tests prove it on file size.

Of course "quality" is subjective ultimately in the end, but the most visual information is in the analog broadcast (not talking about HD of course).

[moyekj]

Ok, I always, ALWAYS get better black color depth on the analog versions of channels.

So much so that if <gasp> I'm watching a live SD channel, I'll flip over to my tv's internal tuner so I can watch the analog broadcast.

In my experience, a properly tuned / correct signal levels version of a SD channel always looks better than its compressed digital SD counterpart. You can bet on it.

Often times people confuse poor signal levels that analog broadcasts show snow as a result, as "worse quality" than the digital SD version. This is because the SD either works or it doesnt or is pixelated. What you don't realize is just how compressed that SD digital channel is. Your own tests prove it on file size.

Of course "quality" is subjective ultimately in the end, but the most visual information is in the analog broadcast (not talking about HD of course). Certainly for analog broadcasts that is the case. However, especially as the 2009 analog broadcast deadline comes about the cable company source broadcasts will be digital instead of analog (at least for the local broadcast channels). For my cable company it's already apparent that many of the channels available in analog tier have a SD digital source and it appears that the analog versions of those channels are decoded versions of the digital ones (presumably done at the headend), so in all respects look worse than the original SD digital versions. That change came about when the cable company implemented Analog/Digital simulcast a couple of years back. Before that time I remember preferring analog versions (with my TV NTSC tuner) much better than the digital ones (with cable box QAM tuner).

[TexasGrillChef]

Ok, I always, ALWAYS get better black color depth on the analog versions of channels.

So much so that if <gasp> I'm watching a live SD channel, I'll flip over to my tv's internal tuner so I can watch the analog broadcast.

In my experience, a properly tuned / correct signal levels version of a SD channel always looks better than its compressed digital SD counterpart. You can bet on it.

Often times people confuse poor signal levels that analog broadcasts show snow as a result, as "worse quality" than the digital SD version. This is because the SD either works or it doesnt or is pixelated. What you don't realize is just how compressed that SD digital channel is. Your own tests prove it on file size.

Of course "quality" is subjective ultimately in the end, but the most visual information is in the analog broadcast (not talking about HD of course).

I agree "Quality" is in the "Eye of the beholder".

Some points I would like to make though...

Sound Quality from a channel, Analog, digital, or even HD is just as important to me in over all Channel quality as the picture itself.

On the test that I ran... DD5.1 is NOT available on the analog channels. To get DD5.1 sound, you have to choose the DIGITAL channel version.

When I went back to compare the quality of the analog recording that was 2.9gb to the digital one that was 1.9gb I did notice a few things.

No "Snow" or "Pixelation" on either recording. The analog recording did have richer color as you suggested. However the DIGITAL version had a SHARPER CRISPER image.

For me.... I value a crisper sharper image over the color richness/depth. In otherwords... if I had to chose between a picture with great color but not very sharp or crips and a picture that was very crisp & sharp but not very good color. I would choose the sharper crisper one.

I realize & understand that other people have different values and some such as yourself prefer a picture with better color that sharpness and detail. Some also don't care about sound quality. Some are even happy with a MONO audio track. Me... I want my DD5.1! :D

You are also correct... by my own "Test" I could very well see that either TWC &/or Discovery channel did obviously compress the program down to a 75% compression rate.

I would have prefered to record "Alaska Experiment" off Discovery HD, However it won't be turned on in my "Sub" area for a few more weeks. It has come to TWC-Dallas.... just each "Sub" area of Dallas gets it as each headend is upgraded. We see it as a channel on our system, but get no picture/sound yet, it's scrambled.

TGC

[TexasGrillChef]

Analog/Digital....

TWC-Dallas area is planning on dropping all analog cable service by the end of 2011. So by then Analog channels will be a moot point.

In February TWC-Dallas will be dropping the "True" analog re-broadcasts of the locals. For their Analog cable customers they will be converting the digital signal to analog. Which means they will still have 3 channels set aside on the system. A Analog (2-99) channel, a digital channel SD broadcast & the HD channel broadcast.

TGC