Google’s ExoPlayer is best in class media player for Android and it supports many features which are not currently supported by stock MediaPlayer.

Best part about Exo is it’s  OpenSource-ness 🙂

In this series of blog posts I’m gonna walk through a couple of useful hacks/customisations on some of Exo components:

• Stats For Nerds – Part 1
• Improved Buffering – Part 2

Find the demo on github which covers both features.

Stats for Nerds:

With Adaptive streaming techniques(HLS, Smooth, DASH), playback is heavily relied on connection speed, meaning resolution changes to adapt to fluctuations in bandwidth which means data consumption varies with time.

As a geek I’ve wondered what’s my n/w consumption, conn speed & sometimes buffer length when I stream a video online. Youtube on Chrome answered these concerns with ‘Stats For Nerd’ mode which depicts all those stats using simple dynamic charts and I found it intriguing. So I decided to do something similar on ExoPlayer and turned out it’s easier than I thought.

Which Stats?

• Connection Speed:
• Network Activity
• Buffer Health
• Dropped Frames
• Video & Screen Resolutions

Code Please

• Connection speed & n/w activity can be obtained by passing BandwidthMeter.EventListener while creating DefaultBandwidthMeter object.

bandwidthMeter = new DefaultBandwidthMeter(mUiUpdateHandler, new BandwidthMeter.EventListener() {
    @Override
    public void onBandwidthSample(int elapsedMs, long bytes, long bitrate) {
        bitrateEstimate = bitrate;
        bytesDownloaded = bytes;
    }
});

• ExoPlayer exposes all available Tracks and their corresponding Formats and setting a Video debug listener will give update you whenever input video format changes. Format is a container of all meta data related to a Video Rendition (width, height, bitrate etc.)
• Dropped frames can be obtained by Video debug listener too.

player.setVideoDebugListener(new VideoRendererEventListener() {
  
    ....
    @Override
    public void onVideoInputFormatChanged(Format format) {
        currentVideoFormat = format;
    }

    @Override
    public void onDroppedFrames(int count, long elapsedMs) {
        droppedFrames += count;
    }
    ......
}

 Buffer health & LoadControl

LoadControl is an Exo Component interface to control buffering of Media and there is a DefaultLoadControl in SDK which takes of when to start buffering and for how long.

We can create our version of DefaultLoadControl with an event listener & a handler to notify player on a buffer data. Check CustomLoadControl class for more info.

player = ExoPlayerFactory.newSimpleInstance(renderersFactory, trackSelector, new CustomLoadControl(new CustomLoadControl.EventListener() {
    @Override
    public void onBufferedDurationSample(long bufferedDurationUs) {
        bufferedDurationMs = bufferedDurationUs;
    }
}, mUiUpdateHandler));
player.addListener(this);

OK. How to draw those awesome charts?

MPAndroidChart is a second to none charting library in Android and it covers all our charting requirements with no exceptions.

Create a Handler to repetitively call to itself every 500ms to update speed & buffer data and N/W activity has to be updated atleast with 1100ms so that updates wont overlap.

private void startPlayerStats() {
    mUiUpdateHandler.removeMessages(MSG_UPDATE_STATS);
    mUiUpdateHandler.removeMessages(MSG_UPDATE_STATS_NW_ONLY);
    depictPlayerStats();
    depictPlayerNWStats();
}

protected void depictPlayerStats() {
    if (!canShowStats())
        return;
    String buffer = DemoUtil.getFormattedDouble((bufferedDurationMs / Math.pow(10, 6)), 1);
    String brEstimate = DemoUtil.getFormattedDouble((bitrateEstimate / Math.pow(10, 3)), 1);
    updateStatChart(player_stats_health_chart, Float.parseFloat(buffer), ColorTemplate.getHoloBlue(), "Buffer Health: " + buffer + " s");
    updateStatChart(player_stats_speed_chart, Float.parseFloat(brEstimate), Color.LTGRAY, "Conn Speed: " + DemoUtil.humanReadableByteCount(
            bitrateEstimate, true, true) + "ps");
    player_stats_size.setText("Screen Dimensions: " + simpleExoPlayerView.getWidth() + " x " + simpleExoPlayerView.getHeight());
    player_stats_res.setText("Video Resolution: " + (null != currentVideoFormat ? (currentVideoFormat.width + " x " + currentVideoFormat.height) : "NA"));
    player_stats_dropframes.setText("Dropped Frames: " + droppedFrames);
    mUiUpdateHandler.sendEmptyMessageDelayed(MSG_UPDATE_STATS, 500);
}

protected void depictPlayerNWStats() {
    if (!canShowStats())
        return;
    updateStatChart(player_stats_nw_chart, (float) (bytesDownloaded / Math.pow(10, 3)), Color.CYAN, "Network Activity: " + DemoUtil.humanReadableByteCount(
            bytesDownloaded, true));
    bytesDownloaded = 0;
    mUiUpdateHandler.sendEmptyMessageDelayed(MSG_UPDATE_STATS_NW_ONLY, 1100);
}

Follow my next blog in series for Part 2 – Improved Buffering.