Thanks for your response, Seven. I collected all my info about this problem into https://github.com/signalwire/freeswitch/issues/955#issuecomment-732425630 and replied to you there.

On Sun, Nov 22, 2020 at 4:53 PM <freeswitch-users-request@lists.freeswitch.org> wrote:

From: Seven Du <dujinfang@gmail.com>
To: FreeSWITCH Users Help <freeswitch-users@lists.freeswitch.org>
Cc:
Bcc:
Date: Sun, 22 Nov 2020 10:49:51 +0800
Subject: Re: [Freeswitch-users] rtmp is sending as 160x120 inset within 320x240 instead of fullscreen
did you happen to set record_concat_video etc ?

or maybe try conference record