It would help if you gave specific make/model of the TV and DirecTV box.
I'm no longer a DirecTV customer, but when I had an HR21, it would output hi-def component and HDMI simultaneously. If yours can do the same, I would feed the Slingbox from the component output, and the TV with HDMI.
If you feed composite video to the Slingbox, it will of course be limited to standard def and not be the best quality. In addition, it's IMO unlikely that the DirecTV box can output composite and hi-def HDMI at the same time, because they would be different resolutions! So, you would either have to switch the output resolution to 480i whenever you wanted to use the Slingbox, or leave it at 480i all the time, which would dumb down the TV to SD also.
> The TV I intend to use the 350 on can only take HDMI input.
> The composite input is fried. Will it work if I have HDMI
> go directly from the DirecTV box to my TV and also composite
> cables going from DirecTV box to my Slingbox 350? I would
> have nothing plugged into the output of the Slingbox.
I've had the following combinations of hardware:
HR20 + Slingbox AV (composite)
HR24 + Slingbox AV (composite and later Monoprice component to composite adapter)
HR24 + Slingbox 350 (component)
All of the above have had a TV with HDMI running directly from the DirecTV receiver.
All the DirecTV outputs will be available when the DirecTV receiver is on--the issue you may see is that since the DirecTV receiver has a HDMI device (TV) attached, if the HDMI device isn't powered on the DirecTV receiver won't send a signal out the component ports when watching HDCP-protected content. You can either 1) turn on the TV or 2) unplug the TV if you need to watch HDCP content.
AFAIK HDCP is only on premiums and I believe PPV. Sports subscriptions (MLB Extra Innings or NFL Sunday Ticket) may be affected as well.
Very helpful, thanks. I plugged everything in as described in the OP and want through setup. On step 4 (test remote) setup would stop and it said "Your Slingbox is in bad state, soft reset your Slimgbox". I would reset it and click "Reconnect" and it would do the same thing. I then unplugged the HDMI from the DirecTV box and tried the setup again....VIOLA! Setup was good.
I then re-plugged the HDMI and everything has worked flawlessly since. Haven't tried any HDCP content. Only thing I worry about is NFL Sunday Ticket but the DirecTV NFL Ticket app works well enough for me.