ec716297 by David LaPalomento

Allow a user-provided initial bandwidth estimate

If the downstream developer has a better way of estimating bandwidth for the initial playlist, use that value.
1 parent 538acc35
......@@ -116,6 +116,13 @@ The number of bits downloaded per second in the last segment download.
This value is used by the default implementation of `selectPlaylist`
to select an appropriate bitrate to play.
Before the first video segment has been downloaded, it's hard to
estimate bandwidth accurately. The HLS tech uses a heuristic based on
the playlist download times to do this estimation by default. If you
have a more accurate source of bandwidth information, you can override
this value as soon as the HLS tech has loaded to provide an initial
bandwidth estimate.
#### player.hls.bytesReceived
Type: `number`
......
......@@ -138,14 +138,21 @@ videojs.Hls.prototype.handleSourceOpen = function() {
};
oldMediaPlaylist = this.playlists.media();
// the bandwidth estimate for the first segment is based on round trip
// time for the master playlist. the master playlist is almost always
// tiny so the round trip time is dominated by latency and so the
// computed bandwidth is much lower than steady-state. to account for
// this, we scale the bandwidth estimate from the master playlist.
// the bandwidth estimate for the first segment is based on round
// trip time for the master playlist. the master playlist is
// almost always tiny so the round-trip time is dominated by
// latency and the computed bandwidth is much lower than
// steady-state. if the the downstream developer has a better way
// of detecting bandwidth and provided a number, use that instead.
if (this.bandwidth === undefined) {
// we're going to have to estimate initial bandwidth
// ourselves. scale the bandwidth estimate to account for the
// relatively high round-trip time from the master playlist.
this.setBandwidth({
bandwidth: this.playlists.bandwidth * 5
});
}
selectedPlaylist = this.selectPlaylist();
oldBitrate = oldMediaPlaylist.attributes &&
......
......@@ -348,10 +348,9 @@ test('downloads media playlists after loading the master', function() {
});
openMediaSource(player);
// set bandwidth to an appropriate number so we don't switch
player.hls.bandwidth = 200000;
standardXHRResponse(requests[0]);
// set bandwidth to a high number, so, we don't switch;
player.hls.bandwidth = 500000;
standardXHRResponse(requests[1]);
standardXHRResponse(requests[2]);
......@@ -507,9 +506,8 @@ test('moves to the next segment if there is a network error', function() {
});
openMediaSource(player);
player.hls.bandwidth = 20000;
standardXHRResponse(requests[0]);
player.hls.bandwidth = 3000000;
standardXHRResponse(requests[1]);
mediaIndex = player.hls.mediaIndex;
......@@ -562,9 +560,9 @@ test('downloads additional playlists if required', function() {
});
openMediaSource(player);
player.hls.bandwidth = 20000;
standardXHRResponse(requests[0]);
player.hls.bandwidth = 3000000;
standardXHRResponse(requests[1]);
// before an m3u8 is downloaded, no segments are available
player.hls.selectPlaylist = function() {
......@@ -579,7 +577,9 @@ test('downloads additional playlists if required', function() {
// the playlist selection is revisited after a new segment is downloaded
player.trigger('timeupdate');
standardXHRResponse(requests[2]);
requests[2].bandwidth = 3000000;
requests[2].response = new Uint8Array([0]);
requests[2].respond(200, null, '');
standardXHRResponse(requests[3]);
strictEqual(4, requests.length, 'requests were made');
......@@ -633,6 +633,22 @@ test('scales the bandwidth estimate for the first segment', function() {
equal(player.hls.bandwidth, 500 * 5, 'scaled the bandwidth estimate by 5');
});
test('allows initial bandwidth to be provided', function() {
player.src({
src: 'manifest/master.m3u8',
type: 'application/vnd.apple.mpegurl'
});
player.hls.bandwidth = 500;
openMediaSource(player);
requests[0].bandwidth = 1;
requests.shift().respond(200, null,
'#EXTM3U\n' +
'#EXT-X-PLAYLIST-TYPE:VOD\n' +
'#EXT-X-TARGETDURATION:10\n');
equal(player.hls.bandwidth, 500, 'prefers user-specified intial bandwidth');
});
test('raises the minimum bitrate for a stream proportionially', function() {
var playlist;
player.src({
......@@ -1268,9 +1284,9 @@ test('resets the switching algorithm if a request times out', function() {
type: 'application/vnd.apple.mpegurl'
});
openMediaSource(player);
standardXHRResponse(requests.shift()); // master
player.hls.bandwidth = 20000;
player.hls.bandwidth = 3000000;
standardXHRResponse(requests.shift()); // master
standardXHRResponse(requests.shift()); // media.m3u8
// simulate a segment timeout
requests[0].timedout = true;
......