MSFT: 50055829 - FFmpegInteropByteStreamHandler is closing the byte stream on failure preventing source resolver rollover

[brbeec]

Why is this change being made?

FFmpegInteropByteStreamHandler is closing the byte stream on failure which prevents the source resolver from rolling over and attempting other byte stream handlers when the MF_RESOLUTION_CONTENT_DOES_NOT_HAVE_TO_MATCH_EXTENSION_OR_MIME_TYPE flag is set for source resolution.

What changed?

I added ByteStreamProxy which can be used to wrap a byte stream and prevent it from being closed unless permitted. It forwards all IMFByteStream calls to the underlying byte stream.

FFmpegInteropByteStreamHandler::CreateMediaSource() uses ByteStreamProxy to wrap the byte stream provided to FFmpegInteropByteStreamHandler::BeginCreateObject() and prevent it from being closed unless the MSS is successfully created and initialized, after which the byte stream will be allowed to close when the media source shuts down.

How was the change tested?

With in-proc WME:

• I verified under a debugger that FFmpegInteropByteStreamHandler no longer attempts to close the byte stream on failure during playback of a corrupted video in Media Player.
• I ran the following TAEF tests:
  • te MF.SourceResolver.unittests.dll /name:SourceResolverTests::TestByteStreamHandlersDontCloseByteStreamOnFailure

[patnels]

I don't understand why we need this. MSS can be used with non ffmpeg bytestreams, do all bytestreams need this code?

[brbeec]

I don't understand why we need this. MSS can be used with non ffmpeg bytestreams, do all bytestreams need this code?

It's because we use MFCreateStreamOnMFByteStreamEx(); the IRandomAccessStream it returns will close its underlying byte stream when it's destroyed.

Internally MF has similar protections to prevent the byte stream from being closed in various scenarios:

• CMediaEngineByteStreamProxy is used for media engine scenarios to prevent the byte stream from being closed by external callers
• CMediaSourceAppServiceConnection uses an internal interface on the IRandomAccessStream returned by MFCreateStreamOnMFByteStreamEx() to prevent it from being closed unless permitted in out-of-proc media source extension scenarios (e.g. out-of-proc WME)