Remote control delay with modulators

Every digital modulator introduces a delay between the input signal (e.g. Foxtel) and what they produce via their RF outputs.

In essence, this is the time it takes for the modulator to decode the signal from an electrical digital HDMI connection, and then convert it to a DVBT radio-frequency digital signal. Depending on the resolution of the input, the bandwidth of the output, as well as whether you’re using MPEG2 or MPEG4/AVC signals all affect the speed of the processing through the modulator. But there is always a delay. Typically, for something like a HD1600-series modulator, this might be anywhere from 0.5s to 1.5s.

Analogue modulators generally had negligible delays (fractions of a second) because converting from an analogue composite AV (yellow/red/white RCA) connection to analogue radio-frequency was a much simpler process. Standard-definition (SD) modulators using MPEG2 (like the RLDM1102) are somewhere between analogue modulators and MPEG4 modulators like the HD1600-series.

Every digital tuner in a TV or set top box also introduces some delay between the RF input, and the HDMI output or producing the image on the actual screen. You see that most commonly in a store with a wall of different televisions showing the same source – some seem to be faster, some slower. They’re all getting the same information, so after that it’s all about how each TV treats the signal – whether they running it through scaling, picture enhancements, smoothing, colour optimisation, and so on.

So when you’re using a remote control through a modulated system, this is roughly the sequence the system goes through:

• Press remote button
• IR blast is picked up by TV IR receiver (roughly instantaneously)
• TV IR receiver converts IR to electric pulses that go back up the RF cabling to the splitter (roughly instantaneously)
• Splitter passes those pulses onto the modulator’s cable and it travels back to the modulator (roughly instantaneously)
• Modulator passes the IR to the Foxtel box, changing the channel (roughly instantaneously)
• The Foxtel output changes on HDMI, into the modulator (roughly instantaneously)
• The modulator decodes, converts and outputs the MPEG4 1080p DVBT signal (from 0.5~1.5 seconds, typically)
• The DVBT signal heads back through the splitter and to the TV (roughly instantaneously)
• The TV decodes the DVBT signal and produces it on the screen (variable time, depending on TV capabilities – anywhere from 0.1~2s typically)

So from when you press the remote control button, through to when the TV shows the change, could be anywhere from 0.5 seconds to up over 3.5-4 seconds.

Delays are part of every modulator system, and there’s no way around that. It’s possible to reduce the delay by using different settings (resolutions especially) or changing to an MPEG2 modulator (like the 1080p LCT1631 which has no IR control capability, or the SD 576i/p RLDM1102 which does have IR).

But there’s no way to reduce that delay to zero, not with a modulator.