Hi Greg, I found it will run without error even if VBR: using kVTVideoEncoderSpecification_EnableLowLatencyRateControl with: VTSessionSetProperties(compressionSession, propertyDictionary: [kVTCompressionPropertyKey_ConstantBitRate: bitrate] as CFDictionary) And it will get error -12900 if set kVTVideoEncoderSpecification_EnableLowLatencyRateControl with: VTSessionSetProperty(compressionSession, key: kVTCompressionPropertyKey_ConstantBitRate, value: bitrate as CFNumber) [quote='857413022, DTS Engineer, /thread/799459?answerId=857413022#857413022'] Are you saying that it has no effect in the sample code you linked to, or in a separate project you have? [/quote] I tried the sample code, and the first several frames were too large and exceeded the size limit. But the following frames seem okay, close to the data rate limit. For low latency live streaming, would you recommend using ABR rather than CBR?

Oh... I write it with other sample it works. Thank you.

Sorry and where is "foundSpatialFormat" used for?

If I modified codes as you provide, it seems to be able to record the spatial video, but the camera preview will stop. After pressing the record button and startRecording, it seems running but no record leave. Maybe we need some more detail for the preview using dualwidth camera

I found the solution is to remove the app on the iPhone, then reboot the iPhone to clear caches. Then build the app into iPhone again.