ZvBox
®
170ConfigurationManual Page11
www.zeevee.com
Rev1.0
SelectUnderscanResolutionstoPresentinVGAEDID
WhenZvBox®170isconnectedtoacomputerviatheVGAconnector,ZvBox®presentstothe
computer’sgraphicscardasetofresolutionsthataresupportedbyZvBox®,includingthe1280x720
resolutionusedbyHDTVs.Theseresolutionsarepresentedina
structurecalledEDID(ExtendedDisplay
IdentificationData).IfZvBox®isbroadcastingafull1280x720resolutiontoanHDTVthat“overscans”
(cropsofftheedgesofthepicture),importantinformationmaybelost,e.g.aPCtaskbarorascrolling
tickeratthebottomofthescreen.Inthat
caseit’spossibletochooseaZvBox®‐supported“underscan”
resolutionatthePC,generatingaslightlysmallerpicturethatwillremainwithintheviewableareaofthe
HDTVscreen.
Thefollowingcommandallowsyoutosetanunderscanresolutionfor720,whichwillbecommunicated
toyourPCviaEDID.Once
anunderscanresolutionhasbeenselected,youmaysetyourPC’soutput
resolutiontothatresolution.
Note:eachTVwillperformadifferentamountofoverscan,sokeepthisinmindwhenselectingan
underscanresolution.ItcanbeusefultohavetheZvBox®outputte st‐image‐1(i.e.“set
video‐source
test‐image1”)whendeterminingthecorrectunderscanresolution.
Syntax
SETVGA‐RES {1264x711|1248x702|1232x693|1216x684|1200x675|
1184x666|1168x657|1152x648|1136x639|1120x630}
MPEG2EncodingControl
Thisgroupofcommandscanbeusedtofine‐tunethecharacteristicsoftheMPEG2encoder.Thefactory
defaultshavebeensettovaluesthatproducethebe stpicture,whilealsomaximizingthechancethat all
HDTVswillcorrectlydisplaytheencodedvideo.WehavefoundthatsomeHDTVsaresensitive
tocertain
thingsliketotalbit‐rateornumberofbitsofDCcoefficients.Thepicturemaysometimesbreakup,orin
somecasesnotdisplayatall!
Experimentingwiththesesettingscanimprovethequalityoftheencodedvideo,butwestronglyadvise
youtotestanychangeson
*eachtypeofHDTV*thatmayreceivethesignal.
SetEncodingBitRate
Adigitalcable(QAM)RFchannelallowsforadatarateupto38.78Mbps.Usually,thatstreamisdivided
intomultipledigitalchannels,eachhavingalowereffectivedatarate.SinceZvBox®isplacingasingle
digitalchannelinthestream,itcansendmoredataduringcomplexscenes,uptothe38.78Mbpslimit.
Thiscanresultinsignificantimprovementsinvideoqualityforcertainverycomplexscenes.However,
someHDTVswillexperiencesomepicturebreakupifthedata rateeverexceeds19.4Mbpsfora
single
digitalchannel.WehaveobservedthatthisistrueofsomeSharpHDTVs,andmaybetrueofothers.
“Normal”willkeeptheencoder’soutputdatarateto19.4Mbps.Highwillallowtheencodertooperate
upto38.78Mbps.Atthistime,LowandNormalhavethe
sameeffect.
Syntax
SETDATA‐RATE{low|normal|high}factorydefault:high