mythplayer: fix exiting playback at EOF

[ulmus-scott]

Fixes #511

This also applies cleanly to fixes/32.

Checklist

• contribution does not duplicate one of our existing pull requests
• contribution is in a branch rebased against master
• code compiles successfully without errors
• code follows the MythTV Coding Standards
• commits are logically organised and have good commit messages

[gigem]

I won't pull this change to master as as as it conflicts with larger, in-progress changes I already have that will be commited soonish. I will include the ultimate fix then or soon after.

I like the change with the short circuit return as the logic is clearer. However, it is provably wrong for the function to return true when there are no frames available. It is likely the clearing of m_buffering that is the important change here. Please verify that doing that and still returning false in fixes/32 fixes the problem. If it doesn't, please keep digging for the underlying bug.

[ulmus-scott]

However, it is provably wrong for the function to return true when there are no frames available.

If it works, and is documented in a comment, it seems fine to me.

PrebufferEnoughFrames() appears to only be called in one place: https://code.mythtv.org/doxygen/mythplayerui_8cpp_source.html#l00646

It is likely the clearing of m_buffering that is the important change here. Please verify that doing that and still returning false in fixes/32 fixes the problem.

It doesn't (tested on master):
With:

    else if (GetEof() != kEofStateNone)
    {
        // other code detects EOF to exit playback, so keep playing
        SetBuffering(false);
        return false;
    }

at EOF, playback is frame-by-frame with each play/pause.

With:

    else if (GetEof() != kEofStateNone)
    {
        // other code detects EOF to exit playback, so keep playing
        SetBuffering(false);
        return m_videoOutput->ValidVideoFrames() != 0;
    }

it stops playback (presumably on the last frame) as before my fix.

With:

    else if (GetEof() != kEofStateNone)
    {
        // other code detects EOF to exit playback, so keep playing
        if (!m_avSync.GetAVSyncAudioPause())
            m_audio.Pause(false);
        SetBuffering(false);
        return m_videoOutput->ValidVideoFrames() != 0;
    }

It sometimes works, but mostly not.

If it doesn't, please keep digging for the underlying bug.

I'll have to try tracing the call(s) to PrebufferEnoughFrames() more fully to determine if/where additional EOF code should go.

[gigem]

Fixed differently.