Media diagnostics · Primary-source explanation; examples are illustrative. Instructions are based on publisher guidance; a UK IPTV account was not tested on this platform.
Ask the capability question precisely
A web recording utility can check a MIME media type before offering it in an export menu. MediaRecorder.isTypeSupported returns a boolean describing whether the implementation should be capable of recording that type. MDN explicitly warns that recording can still fail when resources are insufficient. Keep this result separate from both playback support and a completed recording test. A browser being able to watch a format does not itself answer the recorder capability question.
Preserve the complete requested type
Imagine two test configurations using a general container type and a more specific type which names codecs. Record the exact strings supplied, along with each returned value, rather than collapsing both into a container label. Then note which type was actually used by the recorder. If an application falls back silently, its output extension can conceal the original failed selection. This example describes a comparison design, not a claim that either chosen format works in every browser.
Verify the resulting artefact
For a permitted short local capture, check that data was delivered, recording stopped cleanly and the resulting file plays to its intended end. Record an actual runtime error separately from a negative initial capability result. Keep the original test sample until the export has been checked. The useful conclusion is narrow: capability checking can improve menu choices, while a working recording requires its own evidence; neither observation establishes permission to record a commercial programme.