Improve audio conversion tip (blakeblackshear#2140)

* Improve audio convert guide

* Mention faq in RTMP configuration

* Add example for audio conversion tip

* Change comma to period

* Explain why this is needed

docs/docs/configuration/rtmp.md

@@ -5,4 +5,4 @@ title: RTMP
 
 Frigate can re-stream your video feed as a RTMP feed for other applications such as Home Assistant to utilize it at `rtmp:https://<frigate_host>/live/<camera_name>`. Port 1935 must be open. This allows you to use a video feed for detection in frigate and Home Assistant live view at the same time without having to make two separate connections to the camera. The video feed is copied from the original video feed directly to avoid re-encoding. This feed does not include any annotation by Frigate.
 
-Some video feeds are not compatible with RTMP. If you are experiencing issues, check to make sure your camera feed is h264 with AAC audio. If your camera doesn't support a compatible format for RTMP, you can use the ffmpeg args to re-encode it on the fly at the expense of increased CPU utilization.
+Some video feeds are not compatible with RTMP. If you are experiencing issues, check to make sure your camera feed is h264 with AAC audio. If your camera doesn't support a compatible format for RTMP, you can use the ffmpeg args to re-encode it on the fly at the expense of increased CPU utilization. Some more information about it can be found [here](../faqs#audio-in-recordings). 

docs/docs/faqs.md

@@ -11,10 +11,25 @@ This error message is due to a shm-size that is too small. Try updating your shm
 
 A solid green image means that frigate has not received any frames from ffmpeg. Check the logs to see why ffmpeg is exiting and adjust your ffmpeg args accordingly.
 
-### How can I get sound or audio in my recordings?
+### How can I get sound or audio in my recordings? {#audio-in-recordings}
 
 By default, Frigate removes audio from recordings to reduce the likelihood of failing for invalid data. If you would like to include audio, you need to override the output args to remove `-an` for where you want to include audio. The recommended audio codec is `aac`. Not all audio codecs are supported by RTMP, so you may need to re-encode your audio with `-c:a aac`. The default ffmpeg args are shown [here](configuration/index#full-configuration-reference).
 
+:::tip
+
+When using `-c:a aac`, do not forget to replace `-c copy` with `-c:v copy`. Example:
+
+```diff title="frigate.yml"
+ffmpeg:
+ output_args:
+- record: -f segment -segment_time 10 -segment_format mp4 -reset_timestamps 1 -strftime 1 -c copy -an
++ record: -f segment -segment_time 10 -segment_format mp4 -reset_timestamps 1 -strftime 1 -c:v copy -c:a aac
+```
+
+This is needed because the `-c` flag (without `:a` or `:v`) applies for both audio and video, thus making it conflicting with `-c:a aac`.
+
+:::
+
 ### My mjpeg stream or snapshots look green and crazy
 
 This almost always means that the width/height defined for your camera are not correct. Double check the resolution with vlc or another player. Also make sure you don't have the width and height values backwards.