Quote:
Originally posted by Moorebid There appears to be no information in the HDTV FAQ about either the "traditional" method, or this different method that Fox is/will be using. Care to clarify and/or post the source of information which would explain this? My searches have proven fruitless.
TIA. |
Sorry. I thought I remember Ken H telling someone that it was in the HDTV FAQ.
Anyway, here is a VERY abridged version of what is happening.
The other networks are sending the HD signal (which starts out as1.5 GB) compressed to around 45 mb where the station decompresses it back ot 1.5 GB and then processes it and the recompresses it again to 19.3 mb (or less) then on to your TV. While in the station the audio is then separately deconverted/reconverted in the Dolby 5.1 and then put back in to the data stream. This is where most of the lip sync issues arise.
What FOX is doing is taking that original 1.5 GB signal and inserting Dolby 5.1 while still in its original 1.5 GB form and then compressing to an ATSC compatible 720p format (ASI) 19.3 mb and then on to the stations where that ASI signal is then "spliced" into the stations own 720p stream meaning that the just the data for the stations video and audio are removed and the network data inserted and then it goes to your receiver removing that whole recomress/decompress cycle and even if a station doesn't have Dolby 5.1, since all this splicing happens down stream almost literally at the transmitter input and not back almost at the receiver as with the "traditional method," the video is a better quality and the station doesn't have to have a full HD switching system installed to actually put the network signal on air and still have Dolby 5.1.
I hope I was consistent enough and didn't cut too many corners in explaining it to make sense. I guess I will have to create two diagrams showing the traditional method and the splice method and then put a link to it. A diagram (in this case) IS worth a thousand words. (or more) There are some diagrams that show the FOX splice method, by they are protected by the equipment owners and I don't feel like getting sued for using their original material.