Dischd ch#620 PQ issues?

[shanedude]

Anyone else notice discovery hd ch# 620 on Fios has a lower PQ lately? Looks like TWC with the poor color dithering and mpeg noise between scene changes? Only noticed this on that ch. Compared to Natgeo/History and others I frequent the difference is day and night. If others are not seeing this I will setup for a service call.

[ebo]

I tuned channel 620 and saw what you're talking about within a minute. In the diagnostic menu (Power-OK-OK) I found that it's on RF channel 103. Using an HDHomeRun tuner and TSReader Lite I saw that they're giving its video about 10.8 Mbps which isn't really enough for good MPEG-2 HD. It shares the channel with National Geographic HD which was getting a paltry 8.5 Mbps when I looked. The unused pool (always PID 1FFF, if you're looking) was 18.3 Mbps. So unless they're planning to add more subchannels they're bit-starving both channels for no reason. BTW, a subchannel doesn't need to be unencrypted (and Discovery HD isn't) to see its bitrate

I've seen the same artifacts (very annoyingly) on the FiOS feed of WMHT and not from their OTA feed. Contrary to popular belief, Verizon does compress the local stations more than the stations themselves do. When I compared them just now, WMHT on FiOS was getting 10.8 Mbps while their OTA broadcast was 13.4. All of these numbers are for video only; audio and other streams would take a bit more. Also, they're "eyeball averages" over a few seconds.

[shanedude]

good info ebo! Why are they compressing these chs when they have so much excess video bandwidth? Funny you state that natgeo is sharing with natgeo since natgeo is always crisp.

maybe if enough of us complain about pq on these chs (dischd and wmhthd) they will change something?

[shanedude]

I am confused, they advertise as follows;
'Dazzling, dependable HD picture quality
From brilliant picture quality delivered in uncompressed high definition to greater reliability in almost any kind of weather, it's easy to see why FiOS is the nation's largest 100% fiber-optic network. Simply put, it's the best HDTV experience you can get.'

www22.verizon.com/home/fiostv/

Is this false advertising if you have vivid proof of compression? Anyway we can get the compression stats for these chs from DTV & TWC at similar times for comparison?

[shanedude]

I use a tivo premiere and expect the PQ to be slightly less than live due to tivo compressing the live video and writing to hdd for the live video buffer. That said, since some chs look so nice I know the Tivo can't be a limiting factor in the PQ on some chs compared to others. So, either the feed Verizon receives the channel on has compression and they deliver that feed uncompressed to their customers, or they are adding compression (and claiming not to in advertising).

[ebo]

Back in 2008 when I had TWC I posted a bit rate comparison between TWC and OTA on AVSForum. See www.avsforum.com/avs-vb/showthread.php?p=15050869#post15050869

Nobody delivers uncompressed digital, nor could they. The bit rate would be unmanageably high. So Verizon's claim that they deliver uncompressed high definition is false. The question is whether they compress more or less than other providers (in this area, TWC, OTA, DirecTV and Dish). Also, the quality of the compression hardware can have a big effect. It's possible for one provider to look much worse than another even if they deliver the same bit rate.

Where there are multiple subchannels a statistical multiplexer (stat mux) can make a big difference. Each subchannel is allotted a minimum bandwidth and the stat mux can hand out more as needed from a pool of unused bandwidth. The assumption is that not all of the subchannels will need extra bandwidth at the same time.

I think I read somewhere that most networks deliver a higher bit rate to their affiliates than those stations could broadcast even with a single subchannel. Fox is an exception. Perhaps someone who knows more about that can post details or corrections.

shanedude:
I doubt that your TiVo is further compressing what it receives. Most DVRs don't; they just save it to the HDD. Playback should be exactly as good as what was received.

[xzi]

FIOS doesn't re-compress their signal, they simply pass along whatever compressed signal they receive from that network, so that's what they mean by "uncompressed". A technicality and definitely a lie as far as I'm concerned but still better than the alternatives.

In contrast, Time Warner will compress further the signal to fit into their bit-starved disaster of an MPEG-2 network and DIRECTV will compress everything as MPEG-4 for consistency and bandwidth.

[xzi]

Dec 12, 2011 20:49:13 GMT -5 shanedude said:

I use a tivo premiere and expect the PQ to be slightly less than live due to tivo compressing the live video and writing to hdd for the live video buffer. That said, since some chs look so nice I know the Tivo can't be a limiting factor in the PQ on some chs compared to others. So, either the feed Verizon receives the channel on has compression and they deliver that feed uncompressed to their customers, or they are adding compression (and claiming not to in advertising).

I can't imagine it makes sense for TIVO (or any DVR) to further compress the signal in realtime like that just for space savings--it makes more sense for them to just write out the bits as they come in. Much faster and much less CPU cycles to do it that way.

[shanedude]

XZI, Only reason I feel there is some compression on the tivo is that a 30 min recorded .tivo (mpeg2) program is aprox 15Gb total or 8Mb/s from a source that should avg 12-15Mb/s. I have been playing alot lately with burning shows to DVD. Btw, anyone familiar with how to burn a HD video (h.264 file) to a standard dvd for full HD playback on a bluray player (PS3)? Hoping to convert .tivo to .mp4. Will the PS3 read a dvd holding such a file as is if I just burn the file to the dvd as a data disc rather than video disc?