MediaPlayer mediaStatus field starts in Buffered (=5)

Follow-up on the mediaStatus related issues from: https://bugreports.qt.io/browse/QTBUG-95317

Note: Observations were made using Gstreamer backend.

Observed behavior:

• Upon the creation of the MediaPlayer item (as sampled within Component.onComplete), and before the loading/selection of any source media, the value of mediaStatus starts with a default value of 5, which corresponds to BufferedMedia in Q_ENUM(MediaStatus).
• After setting the source URL to a valid video file, the status changes in the following sequence:
  • BufferedMedia (5)
  • NoMedia (0)
  • LoadingMedia (1)
  • LoadedMedia (2)
• Upon clicking play, the media status changes to BufferedMedia (5)
• Upon stopping the video, the status returns to LoadedMedia (2)
• Upon setting the source url to "", the status returns to NoMedia (0).

Expected behaviors:

• MediaPlayer status should start with a NoMedia (0) value.
• The status should never reflect any state other than NoMedia if the source url is empty
• The BufferedMedia status should probably be preceeded by the BufferingMedia status? This may not be an issue in that it may happen all in one tick in certain situations so BufferingMedia essentially appears to be skipped.

Methods to reproduce in qtmultimedia/examples/multimedia/video/mediaplayer:

• Add the following debug statements to the MediaPlayer in main.qml:

    MediaPlayer {
        id: mediaPlayer
        videoOutput: videoOutput


        audioOutput: AudioOutput {
            id: audio
            muted: playbackControl.muted
            volume: playbackControl.volume
        }

        onErrorOccurred: { mediaErrorText.text = mediaPlayer.errorString; mediaError.open() }
        onMetaDataChanged: { metadataInfo.read(mediaPlayer.metaData) }

        // Debugging
        onSourceChanged: {
            console.log( "Source changed: " + source )
        }

        onMediaStatusChanged: {
            console.log( "Media Status: " + mediaStatus + " Playback State: " + playbackState )
        }

        Component.onCompleted: {
            console.log( "Setting source to empty" )
            source = ""
        }
    }

• In PlayerMenuBar.qml, comment out the stop() and play() calls in FileDialog.onAccepted() to prevent automatic state changes and allow us to see things at a more fine-grain level:

    FileDialog {
        id: fileDialog
        title: "Please choose a file"
        onAccepted: {
            // mediaPlayer.stop()
            mediaPlayer.source = fileDialog.currentFile
            // mediaPlayer.play()
        }
    }

• In PlaybackControl.qml, add a "source reset button" beside the AudioControl item:

RoundButton {
                    id: resetButton
                    radius: 50.0
                    text: "Src=''";
                    onClicked: {
                        console.log( "resetting source" )
                        mediaPlayer.source = ""
                    }
                    anchors.right: audio.left
                    anchors.top: audio.top
                }

Then to produce the results:

1. Launch the program. The following should be printed:

QML debugging is enabled. Only use this in a safe environment.
qml: Setting source to empty
qml: Media Status: 5 Playback State: 0

2. Load a video.

qml: Media Status: 0 Playback State: 0
qml: Media Status: 1 Playback State: 0
qml: Source changed: file:///home/spiderkeys/cave/cave_3.mp4
qml: Media Status: 2 Playback State: 0

3. Click play.

qml: Media Status: 5 Playback State: 0

4. Click pause.

5. Click the "source reset" button to set the mediaPlayer.source=""

qml: resetting source
qml: Media Status: 2 Playback State: 0
qml: Media Status: 0 Playback State: 0
qml: Source changed: