fix: SG-42334: Fix random crashes involving SoundTrackIPNode

[bernie-laberge]

fix: SG-42334: Fix random crashes involving SoundTrackIPNode

Linked issues

NA

Summarize your change.

• Fixed race conditions in SoundTrackIPNode that caused random crashes due to unsynchronized access to m_fb across threads.
• evaluateAudioTexture() now uses a short lock-around-read pattern to safely snapshot m_fb before use, and re-checks it under lock before dereferencing to construct the
  IPImage — guarding against propertyChanged() clearing m_fb on the main thread between the two access points.
• propertyChanged() now acquires m_fblock before allocating or restructuring m_fb, preventing data races during waveform texture resize.
• clearFB() now acquires m_fblock for the duration of the pixel clear and stats reset, making it fully thread-safe.

Root Cause

m_fb (the waveform framebuffer) was read and written from multiple threads without synchronization. evaluateAudioTexture() ran on the audio/render thread while
propertyChanged() and clearFB() ran on the main thread. A m_fb pointer that was valid at the check could be freed mid-use, leading to use-after-free crashes.

Describe the reason for the change.

Random crashes had been reported originating from SoundTrackIPNode.

Describe what you have tested and on which operating system.

Successfully tested on macOS.

Test Plan

• Enable the Timeline Magnifier via the RV/Tools/Timeline Magnifier menu
• Load media that contains audio
• Play media with audio waveform display enabled and rapidly scrub / resize the timeline — no crash
• Trigger property changes (e.g., resize the waveform panel) during active audio playback — no crash

Add a list of changes, and note any that might need special attention during the review.

If possible, provide screenshots.

[Copilot]

Pull request overview

Fixes random crashes in SoundTrackIPNode by adding synchronization around waveform framebuffer (m_fb) usage and by centralizing the default audio packet size into a shared constant.

Changes:

• Add mutex protection around m_fb allocation/restructure/clearing and re-check m_fb under lock before dereference in evaluateAudioTexture().
• Introduce TWEAK_AUDIO_DEFAULT_PACKET_SIZE (2048) and replace hardcoded packet-size defaults across audio/cache/movie components.
• Update IPGraph to use the shared default packet size instead of platform-specific hardcoded defaults.

Reviewed changes

Copilot reviewed 8 out of 8 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
src/lib/ip/IPCore/SoundTrackIPNode.cpp	Adds locking around framebuffer access/clear and re-checks m_fb before creating the waveform IPImage.
src/lib/ip/IPCore/IPGraph.cpp	Uses TWEAK_AUDIO_DEFAULT_PACKET_SIZE for m_audioPacketSize and includes TwkAudio/Audio.h.
src/lib/image/MovieRV_FBO/MovieRV_FBO/MovieRV_FBO.h	Replaces default audioPacketSize argument with TWEAK_AUDIO_DEFAULT_PACKET_SIZE.
src/lib/image/MovieRV_FBO/MovieRV_FBO.cpp	Updates member default m_audioPacketSize to TWEAK_AUDIO_DEFAULT_PACKET_SIZE.
src/lib/image/MovieRV/MovieRV/MovieRV.h	Replaces default audioPacketSize argument with TWEAK_AUDIO_DEFAULT_PACKET_SIZE.
src/lib/image/MovieRV/MovieRV.cpp	Updates member default m_audioPacketSize to TWEAK_AUDIO_DEFAULT_PACKET_SIZE.
src/lib/audio/TwkAudio/TwkAudio/Audio.h	Defines and documents TWEAK_AUDIO_DEFAULT_PACKET_SIZE (2048).
src/lib/audio/TwkAudio/AudioCache.cpp	Uses TWEAK_AUDIO_DEFAULT_PACKET_SIZE as the default cache packet size.