Suena a un problema de EDID Handshake. Si al actualizar los drivers de la gráfica no se soluciona y no te atreves o te da pereza probar lo que comenta MDLSoft puedes probar a capturar el EDID y crear un controlador nuevo para el AVR-TV. Echa un vistazo a esto:
EDID Overrides to solve bitstreaming issues for ATI 5xxx's - AVS Forum
La solución a la que enlaza:The problem with the driver reverting to 2 channel audio (or no audio) due to hotplug detection (switching inputs on TV or AVR, HTPC waking from sleep, or powering up order of components)*can be fixed by following the procedure explained by Ryan L in this post.
*Workaround * Nvidia HDMI audioAnyway, download MonInfo (Monitor Asset Manager 2.7) from here (download link is on the left). I made sure that my PC was booted up correctly and able to configure multiple speaker configurations in the sound control panel. Started the MonInfo program, select file on the top left and create an INF. This should make an INF of your display + receiver. Take note of where you save it to. Now open up device manager, navigate to monitors, and then select your display device (it's probably named generic display device) and click update driver software. You want to browse my computer for driver software and then let me pick from a list... select the INF you created earlier. Reboot, done.
I tested this out a bit and everything is working the way I want it to so far (desktop icons stay in place, audio options don't drop to 2 channel when switching inputs or if I turn on the TV first by accident, etc etc). This fix should work the same way for NVidia GPUs too - I believe that any change in audio/video drops audio altogether in most cases with Nvidia.
Se trata de capturar con el programa Moninfo el EDID de tu AVR y TV cuando todo está bien, es decir tienes sonido e imagen ok.
http://www.entechtaiwan.com/util/moninfo.shtm
Es mas fácil de lo que parece, en File le das a Create INF y este INF es el que utilizas para actualizar el controlador de tu TV-AVR.
Aunque no es tu mismo caso y no tienes que seguir los mismos pasos, te dejo una explicación en español a un compañero con un problema de EDID por si alguna explicación te sirve de ayuda:
https://www.forodvd.com/tema/130495-...ml#post1304494
Si esto tampoco te funciona otra solución sería tapar el pin 19 del cable HDMI:
EDID Override Thread - Page 71 - AVS Forum
Y ya por último las soluciones comerciales comentadas.