Fix RTP stream shutdown crash

[aleksandr-voitenko]

Description

Fixing the following crash

EXCEPTION_ACCESS_VIOLATION_READ / 0x0
Fatal Error: EXCEPTION_ACCESS_VIOLATION_READ / 0x0

obs-outputs    +0x3d81    encoder_video_codec (flv-mux.c:156)
obs-outputs    +0x3d81    build_flv_meta_data (flv-mux.c:216)

Motivation and Context

The crash happens in RTP stream internals (flv mux, in this case) on shutdown during a reconnect attempt. There is a data race on encoders of an output, and while it tries to build meta data without any checks on encoder existence and/or locking any mutexes, some other thread resets them. There are clues in logs (see also Sentry reports):

   crash!
  "[000:00:15:29.331.776.100][4440][Info] [rtmp stream: 'main_stream_first'] Socket send buffer is 65536 bytes\n",
  "[000:00:15:29.331.515.500][4048][Debug] obs_encoder_get_codec: Null 'encoder' parameter\n",
  "[000:00:15:29.331.514.300][4048][Debug] obs_encoder_get_height: Null 'encoder' parameter\n",
  "[000:00:15:29.331.513.100][4048][Debug] obs_encoder_get_width: Null 'encoder' parameter\n",
  "[000:00:15:29.331.510.100][4048][Debug] obs_encoder_video: Null 'encoder' parameter\n",
  "[000:00:15:29.331.419.200][4048][Info] [rtmp stream: 'main_stream_first'] Connection to rtmps://push-rtmp-l11-sg01.tiktokcdn.com:443/game (43.152.140.130) successful\n",
  "[000:00:15:28.974.208.000][6820][Debug] signal received: stopping streaming\n",

In this case a good solution is to retain encoders and allow to finish building meta data, even though it will be discarded immediately.

How Has This Been Tested?

Manually, Windows only.

Types of changes

• Bug fix (non-breaking change which fixes an issue)