Instant channel changes.

[Lurendrejer]

I'm guessing most of us have multiple tuners. Is there a technical reason why no PVR backends uses the "next" available tuner to pretune the "next" channel in the frontends list to have near-instant channel changes?

Thank you for a great piece of software

[sub]

You're never going to get instant channel changes with a scheme like that. You have no idea if the what channel the user is going to tune to, so you're still going to wear the time of the device tuning, finding the audio/video stream and the wait for the next iFrame to go by in the stream before the video decoder will display it.

How quickly your channel is will depend on the device you're using, and some of the encoding settings used by your broadcaster (GOP size etc). My channel changes in NextPVR average about a second on our DVB-S system here in New Zealand, which is as-fast, or faster than most set top boxes. Its unlikely it'll ever be any quicker.

[Lurendrejer]

I'm using DVB-C and my changes are "almost instant".
I just find terms like, almost instant is gibberish. Like more silent. Either it's instant/silent or far from it.

In my case i have three tuners doing nothing most of the time. Except when there are multiple frontends watching live-tv.

I don't use channel up/down simply because it is persieved as slow (compared to, lets say 1990's over the air tuning.) I always use the TV-guide, because changing the channel up three times just feels sluggish.
If the three tuners were put to good use, when i pressed the "up" button once, the next two tuners would already be buffering the next two channels, maybe just even for a few seconds if i decide not to change up again. I know that this would require more frontend/backend chit-chat and all sorts of things.

The technical reasons that you mentioned are quite valid, but you don't really take into account that my buffering drive can handle 20-40 streams and my tuners are just sitting there. Doing squad-diddly-doo

I know there are considerations like power, heat, etc. But thats not really up to the PVR-software to take into account. I've always wondered why this functionality isn't found anywhere, not even in high end tv-sets with multiple tuners. It could really set a piece of software appart from the rest.

[sub]

Hardly anybody just uses channel +/- to switch between channels these days, ever since the move to digital (and/or set top boxes) with multi-second channel change times, and so many channels available and usually piles of crap channels between the good ones. Most people just type the channel, or use the guide to switch channels.

You'd need at least three tuners for what you describe, which not many people have. Even if you had the three tuners covering the current channel, channel above and channel below, you'll still going to have to wait for the iframe before the video decoder will display a frame, which can be up to a 1.0 or 1.5 seconds on some broadcasters.

I honestly don't see me doing anything on this. I like to keep channel changes as quick as possible, but this is just not worth the effort. Sorry.

[Lurendrejer]

I'm probably being stupid now, but you kind of proved my point by mentioning multi-scond channel changes.

I can filter the channels, and i do. I need two HDhomeruns for my four frontends, but most of the time i could have two tuners already pre-buffering the channel above and below the one I'm watching. If the backend circled the tuners instead of waiting for one device it would be channel-changing-instant-party all the time. About it being worth the effort, i can se that. But that doesn't stop everyone, and it seems to me that it has never been done, which baffles me. I've had my hands on stupidly expensive tv sets (not my own, I'm poor) and they still don't even try to do something smart like fading between channels or neat transitions like any phone does between every action you do.

Thank you for the replies, and i'm still hoping that someone, some day will be doing what phones and macs have been doing for years with transitions. Fooling people into thinking they are fast and fluid.

[whurlston]

Typically, the actual channel change occurs before you even lift your finger off the remote. The delay is (as sub said) is usually the decoder waiting for an I frame to display. This delay will happen whether it's a channel change (current process) or a stream change (your proposed process).

You should try a different decoder if channel changes are too slow for you. Not all decoders are created equal. I have found Cyberlink to be one of the fastest.

[Lurendrejer]

If the video was already being buffered, wouldn't i be possible to send an iframe almost instantly to the frontend?
Maybe even just use the stream already being played.

Channel changes are not too slow, not at all - Like I mentioned, i'm just curious to why people don't try doing more, if it is in any way possible. It might not be possible, but someone quite often tries to reach for the stars.

[stustunz]

It's simple buy more tuners record every program you might want to watch then there is not a reason to change channels or watch live tv anymore

This is how I do it

[sub]

I'm probably being stupid now, but you kind of proved my point by mentioning multi-scond channel changes.

Yep, but I wasn't talking about NextPVR here - I was just saying it's a world where people are accustomed to multisecond channel change times, on their TVs and set top boxes etc, so very few people sit there and press the Channel-/+ buttons these days, particularly given people have so many channels these days, and there is a lot of crap channels in between the good ones. Most people are more accustomed to using a direct channel number, or a TV Guide to change channels. ie, not sure if it'd even be used if it had this feature. People don't typically do this these days, and no point in pressing ch+ 12 times to get to the next good channel.

[sub]

If the video was already being buffered, wouldn't i be possible to send an iframe almost instantly to the frontend?
Maybe even just use the stream already being played.

Unfortunately the decoding/playback (at least on Windows) doesn't work that way. Audio is often encoded significantly ahead of the video in the streams generated by the broadcasters, and Windows buffering and timing is all based the audio stream. If you start playback of a stream immediately before an iframe, you typically wont see that frame, and will have to wait until the next one.