When pushing a stream without audio, the HLS stream contains abnormal audio encoding information.

[yang-441]

Describe the bug
When streaming video without audio to SRS via the RTMP protocol, the resulting HLS playback anomalously contains audio information, causing compatibility issues with some players. By adding the configuration 'hls_acodec an', the aforementioned anomaly can be resolved without affecting video streams that contain audio. Should we consider making 'hls_acodec an' the default value?

step1:
Using the RTMP protocol, push a video stream without audio to the SRS service.

step2:
While playing an HLS stream through VLC, it was discovered that the stream contains abnormal audio information.

step3:
Add the configuration: hls_acodec an.

step4:
Upon restreaming, it was observed that the abnormal audio information had disappeared.

step5:
Push a video stream with audio and test whether setting hls_acodec to 'an' will have an effect.

Version
Version number: SRS/5.0.x, 6.0.x, and so on.

TRANS_BY_GPT4

[suzp1984]

I think hls.hls_acodec and hls.hls_vcodec can be deleted, the srs can adjust the hls video and audio codec very well, just like hls.hls_acodec an; hls.hls_vcodec vn; did.