BBS:      TELESC.NET.BR
Assunto:  Re: A/V problems while the Pi is doing nothing
De:       Jim Diamond
Data:     Tue, 17 Mar 2026 10:30:02 +1100
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On 2026-03-15 at 23:10 ADT, ottitale  wrote:
> Jim Diamond  at 15.3.2026, 21:51:44 "A/V problems while the 
> Pi is doing nothing":
>> On 2026-03-15 at 03:29 ADT, ottitale  wrote:
>>> Jim Diamond  at 14.3.2026, 23:57:15 "A/V problems while the
>>> Pi is doing nothing" :

>>>> I have a RPi5 hooked up to a TV, and I watch movies or TV programs or what
>>>> have you by streaming them on the Pi and sending them to the TV via HDMI.

>>>> I assume this is something that most of you have done at some point.

>>>> I turn the TV off (really it goes into its low power mode) and leave the
>>>> RPi on.

>>>> Occasionally, when I turn the TV on to watch something, there are two
>>>> things wrong:
>>>> (1) The video no longer matches the TV screen size (1920x1080 in this case).
>>>> The video is slightly larger, in that the edges of the picture are
>>>> off-screen.
>>>> (2) The sound is no longer coming through the HDMI (or, at least, the TV
>>>> remains silent).

>>>> I can get things working again by running the command
>>>> xrandr --size 800x600  ;  sleep 1 ; xrandr --size 1920x1080
>>>> (I have no idea why this gets the sound working.)

>>>> Having a work-around is fine, but I'm wondering if anyone else has seen
>>>> this issue.  I don't know whether it is
>>>> -> a Pi hardware issue
>>>> -> a Pi software issue, or
>>>> -> a glitch in my TV (Sony Bravia, FWIW).

>>>> Anyone?

>>> This problem occurs when there is a conflict with CEC. The Pi then
>>> disables CEC for HDMI. The TV get no Information -> Standard values that
>>> do not fit.

>> Hmmm... CEC conflicts are a new one for me.

>> The Pi and the TV are the only devices in the vicinity (and thus the Pi is
>> the only HDMI input for this TV).  Is there a possible CEC conflict in this
>> case?

> Yes, the TV needs a signal to informa pi that CEC is on, pi wants this 
> signal but if no signal is detected the CEC is changed to "off".

> There are some packages for CEC to start a cron to activate CEC again.

Thanks for the info.  I'll try tracking this down and see if it has any
effect.  Unfortunately (maybe) the problem is quite sporadic, and I don't
know how to trigger it, so testing whether something fixes it is more
statistical than definitive.

                                Jim


--- PyGate Linux v1.5.13
 * Origin: Dragon's Lair, PyGate NNTP<>Fido Gate (3:633/10)

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