I am working on a functionality explained below-
Once a video is loaded/with a button click, it has to play in reverse. The target devices are smart phones and tablet devices. I am trying to do this using HTML5 tag and read about the playBackRate attribute. Further down, I am using the HTML5 stuff to generate my mobile apps using Phonegap.
Here's a link I found interesting but partially working -
http://www.w3.org/2010/05/video/mediaevents.html
The playbackrate, when changed doesn't do anything except it pushes the video back, by whatever number is given there.
I read it here that when playBackRate is set to -1, the reverse playback should happen.
I am not clear on how to exactly implement this. Does the playbackrate actually do this reversing? or should I opt on doing something else?
NEW LINE HERE:
I am almost there.. found a working example here. But this is not working when I am trying it on my system. I am not sure where I am making it wrong.
This is an old thread so I'm not sure how useful the following will be.
The Mozilla developer notes point out that:
Negative values [for playbackRate] don't currently play the media backwards.
Same goes for Chrome, but Safari on Mac works.
This page from w3c is great at observing and understanding events:
http://www.w3.org/2010/05/video/mediaevents.html
I took the jsfiddle you mentioned and added some extra controls for fast forward/rewind speeds:
http://jsfiddle.net/uvLgbqoa/
However, though this works fine for me with Chrome/Firefox/Safari, I should point out that it doesn't really address your key questions.
Firstly, the approach assumes that negative playback rates don't work (which at the time I write this, is largely true AFAICS). Instead, it fakes it by calculating and setting the current time in the video:
function rewind(rewindSpeed) {
clearInterval(intervalRewind);
var startSystemTime = new Date().getTime();
var startVideoTime = video.currentTime;
intervalRewind = setInterval(function(){
video.playbackRate = 1.0;
if(video.currentTime == 0){
clearInterval(intervalRewind);
video.pause();
} else {
var elapsed = new Date().getTime()-startSystemTime;
log.textContent='Rewind Elapsed: '+elapsed.toFixed(3);
video.currentTime = Math.max(startVideoTime - elapsed*rewindSpeed/1000.0, 0);
}
}, 30);
}
Chrome handles this quite seamlessly, even playing snippets of audio as it goes.
Secondly, I think you want to play the video in reverse as soon as the page loads. I can't imagine a use case for this, but the first issue I see is that the whole video will need to be downloaded prior to playback, so you'll need to wait - but download probably won't happen until you start playing. So you could set the currentTime to near the end and wait for the canPlay event, and then start playing in reverse. Even then, this seems very awkward.
I think there are these broad options:
Use a native video widget rather than HTML. I'm guessing (without checking) that the native API supports reverse playback.
Generate a proper reversed video and play it as normal. For example, on a server somewhere use a program like ffmpeg to reverse the video. Then your app downloads the video and plays it normally, which looks to the user like reverse.
Assuming it really does make sense to have an application that plays a video in reverse when you load it, then I'd personally go for #2.
Related
I have a Netflix account and I have peeked under the hood at its video player running inside Google Chrome. Netflix calls its video player "Cadmium" and the javascript exposes all the functions and event handlers you might expect, such as play, stop, pause, mute, etc. I'm building a little Chrome extension that would enable me to call these Cadmium player function, but the hard part for me is figuring out how to create an instance of the player so I can start calling. The javascript is large, complex, and somewhat obscure. Once I can create an instance of that player, I'm thinking that making calls into the functions will be easy.
Here is a relevant chunk of js:
muteOn: function() {
this.savedVolume = this.getVolume(),
this.updateVolumeDisplay(0),
this.scrubber.updatePercent(0),
this.muted = !0,
this.videoPlayer.setMuted(this.muted)
}
In Chrome dev tools I can set a breakpoint inside that block, and execution hits the breakpoint when I click the Mute button on the netflix video player. The Netflix js is (unsurprisingly) heavily obfuscated via method renaming. I tried stepping through the code in the debugger and ended down a hundred rabbit holes, never able to find my way to the top of the stack, so that I could make that same call (at top of stack) to simulate the user clicking the mute button. I also tried the approach of programmatically clicking the mute button on the UI player, which would meet my needs equally well, but they have serious defensive mechanisms in there, spinning me like a top.
Since there are over 100K lines of javascript, and I'm uncertain which chunks exactly would be relevant for this post, I would like to suggest that you load Netflix in Chrome, open dev tools, play a movie, and inspect the pause or mute button. Interacting with those video player controls takes you into the maze of javascript which I'm trying to see how I can tap into to control aspects of the player programmatically (just from dev tools is fine for now). Another important thing I need to figure out is how to query the video player to determine the current elapsed time of the playing video.
Any ideas how I can crack this nut? (Thanks in advance!)
Using Chrome, I get playback using HTML 5 video.
Once you get a hold on the <video> tag element, you can use the HTML 5 video API:
Get the <video> element
var video = document.evaluate('//*[#id="70143639"]/video',document).iterateNext()
70143639 is the id of the video, as in https://www.netflix.com/watch/70143639
Remaining time (HH:mm)
document.evaluate('//*[#id="netflix-player"]/div[4]/section[1]/label', document).iterateNext().innerHTML
Elapsed time (seconds)
video.currentTime
Elapsed time updates
video.addEventListener("timeupdate",
function(e) {
console.debug("Seconds elapsed: ", e.timeStamp/1000/60);
}
);
Note that I don't get the same results as with video.currentTime, you may need to use an offset based on the difference. Also it may be something explained in the spec: https://www.w3.org/TR/html5/embedded-content-0.html
Play
video.play();
Pause
video.pause();
Go back and forth in time
Courtesy of rebelliard:
netflix.cadmium.UiEvents.events.resize[1].scope.events.dragend[1].handler(null, {value: 600, pointerEventData: {playing: false}}); where 600 is the number of seconds to seek.
Note that I ran into "Whoops, something went wrong..." using this:
video.currentTime += 60;
Even with pause and play calls. This is what this demo page does, you nay need to read the full spec on seeking.
Mute and get muted status
video.muted = true
Like video.currentTime, this is a writeable property.
I'm implementing a video player using VideoJS. Two key functions of this video player are:
a) If the user leaves the page, resume the video at that point when they come back or on refresh
b) Include HLS (h.264/mp4) support to provide better video quality depending on the connection.
The API for saving and retrieving a user's timestamp is already in place, and using the excellent HLS plugin, the video player works almost fine in all browsers as expected. The following code is used to initialize the player and jump to the saved time:
videojs.options.flash.swf = '../video-js/video-js.swf';
var player = videojs(videoId);
supportHLS = videojs.Hls.isSupported();
player.ready(function() {
[[event listeners for media controls]]
this.on('seeked', function() { console.log('seeked');});
this.on('seeking',function() { console.log('seeking');});
var PLAYER_LOADED = 'loadedmetadata';
if(!supportHLS) { PLAYER_LOADED = 'canplay';}
this.one(PLAYER_LOADED, function() {
this.one('canplay', function() {
this.play();
});
this.currentTime(savedPosition);
lastViewed = savedPosition;
});
});
(Reason for the roundabout logic: Chrome had issues with playing the video before the new data (after the seek) had loaded, which caused a number of problems with the data in the buffer. Also, Safari 7.1 would break if you tried this during the 'loadedmetadata' event)
However, there's still one problem, specific to Safari. The loading spinner doesn't always go away when you refresh the page. Examining the logs and listeners seems to indicate that the 'seeking' and 'seeked' events fire at about the same time, but in different orders; the problem always arises whenever 'seeked' fires first, and never occurs when 'seeking' is first. Furthermore, any seeking after the video is playing removes the spinner, so it has to be caused by the initial seek.
It's interesting that Safari supports HLS streaming natively, yet consistently causes the most problems with this player implementation. This is the last Safari bug to iron out, but though it's small it still has a negative impact on user experience.
What causes Safari to fire the 'seeked' and 'seeking' events out of order like this? What can I do to work around it, or is there a cleaner solution for what I'm trying to accomplish?
I have created a set of custom navigation elements for a video, to simulate walking around a building (for fire training).
When an overlay is pressed, the routine jumps to a predetermined spot using vidElmt.currentTime = 5; (for example). This works fine on Windows (Chrome, FF, and IE 11) and on the iPad (Safari), but when I try it on my Android phone (4.3, using Chrome or the built-in browser), the videos jump to the wrong spots. For example, if I set it to jump to the 5 second spot, it looks like it jumps to 2, 3 or 4 second spot.
I know some people may point out that I could be trying to jump to a spot not yet loaded, but I know the parts of the video I'm jumping to are definitely already loaded.
I wonder if it's something about my video format (mp4). I've searched to see if anyone has problems with the video tag and currentTime on Android, but I'm not finding anything.
Here is my demo link, if you want to check it out for yourself: http://eqsim.com/fesim/ when the playhead arrives at side/location, it should loop that specific section, and you can press the arrow keys that are lit up to change locations.
I'd appreciate any suggestions!
-jonathan
I suspect you might need to keep querying the video in an interval until the frame you want is seekable. A full working example can be found in this jsbin, but the relevant code is this:
function isSeekable(time) {
for (var i=0; i<video.seekable.length; i++) {
if (video.currentTime > video.seekable.start(i) && video.currentTime < video.seekable.end(i)){
return true
}
}
return false
}
Does that work for you? It seems to work in my Android 4.3 stock browser. If not, can you tell me more about how you encoded your video? Adding more keyframes could help with frame accuracy.
I'm working with HTML5, making an audio player.
I wonder to know how I can add a buffer bar so that the user can see how long the song is loaded.
I've tried using several properties that I saw in some tutorials, but none have worked, and I can not find anything about this specific topic.
This is the audio player that I'm trying to edit.
I wish someone could guide me on how to edit the code to do it, or, otherwise, recommend tutorials, documentation or any information.
There's no guarantee that all of this is going to work on all browsers...
...however, assume, for the rest of this post that:
var audio = new Audio();
audio.src = "//example.com/some-really-long-song.mp3";
"canplay" is the first useful event, in terms of being able to play the song.
It means that part of the song is ready to go, and it's at least enough to be able to hear something, if you hit the play button.
Alternatively "canplaythrough" is the browser's guess at whether you can start playing the song right now, and it will run without stopping (based on amount of data left to download, and how fast the song is currently downloading).
audio.addEventListener("canplay", function () { audio.play(); });
"durationchange" is an event which should fire when a duration changes.
For file-types which don't have metadata, or where the metadata isn't supported, the whole duration might not be available as the file starts loading.
In these cases, audio.duration might be updated by the browser downloading the first bit of the media, and then the last, and making an educated guess at the length of the file, or the duration might come from the browser having to load more and more of the file, and increasing the duration as it goes. Where we are in terms of support, I don't know.
audio.addEventListener("durationchange", function () {
player.time.duration.update(audio.duration);
});
"progress" is an event which fires ~250ms as data is coming in (while downloading the file).
progress tells you that updates have been made to data which is available to seek through right now.
This makes it a good event to use to check your audio.buffered objects, in order to update the "loaded" portion of your progress bar.
audio.addEventListener("progress", function () {
player.progressBar.update(audio.buffered.start(0), audio.buffered.end(0));
});
Then you can use "timeupdate" to deal with playback.
timeupdate will update a few times a second, as the song is playing (as audio.currentTime moves forward).
I am using jQuery 1.5 and jPlayer 2.0.0, please ignore the fact that this is going to auto play music, I am going to supply enough warning before it starts, the user has to press a big button to initiate the page and I will provide a big STOP button.
I would like the audio file to begin playing and a function be called after the page is ready and the audio is loaded.
I have the following javascript (I have modified the code so it can be understood better).
function FemeMusic() {
FemeMusic.prototype.addMusic = function(actionAfterMusic) {
$("#jp").jPlayer({
ready: function() {
var jPlayerElement = $(this);
jPlayerElement.jPlayer('setMedia', {
mp3: 'aSongByJamesBlunt.mp3'
});
jPlayerElement.bind($.jPlayer.event.progress,
function(event) {
if (event.jPlayer.status.seekPercent === 100) {
jPlayerElement.jPlayer("play");
}
if (actionAfterMusic) {
actionAfterMusic.call();
}
});
},
swfPath: "/flash",
preload: "auto"
});
}
}
I have this function to trigger the above code.
$(document).ready(function() {
var femeMusic = new FemeMusic();
femeMusic.addMusic(killMyself);
});
I was using the same code but with the $.jPlayer.event.loadeddata event without the if statement instead of $.jPlayer.event.progress and it worked fine in some browsers but isn't compatible when it comes to using flash because it doesn't fire the event (Also I had a problem with it in firefox 3.5 but I don't know why). The above seems to work in Firefox
I read this
"I suggest you use the progress event instead and check that the:
event.jPlayer.status.seekPercent === 100. "
On this post http://groups.google.com/group/jplayer/browse_thread/thread/9dc9736f9d6947bd?pli=1 by the creator
Any one got any suggestions?
Edit
Having not got this working in chrome and safari I tested this on a new version 3.6 of Firefox (which I should have done in the first place) and it worked as expected, despite the fact that in the documentation event.progress id described as:
A robust jPlayer event supported by Flash and HTML5 browsers
and in the link above the creator suggests to use event.progress to get round browser problems I can only assume it's a browser specific issue.
Would be nice to get some clarification on this though.
From the creator of jPlayer:
So your goal here is to auto-play AFTER the media is buffered?
If you want the short answer. Forget it. x-browser buffering is a mine
field. Some simply ignore it as you have found. Just setMedia and play it.
If you really want to try and do it. Then a play then pause would help,
since a media.play() is better x-browser than a media.load() i.e. its
operation varies less. The iOS Safari would ignore the play completely
though. The user would need to click on something that starts the
operation i.e. a play button.
That last point applies to trying any form of autoplay, so ensure that there
is a play button available. The jPlayer interface will cope with iOS not
playing through feedback from the browser events i.e. stalled.
I had problems with the progress event with flash and html5 backend in most browsers. as far as I can see the timeupdate event is working much better.