Hi Don,
What I was saying was that FLV streamed with RTMP is the way to serve
them all iOS, Android, Windows, Mac and Linux. It would even work on
Blackberry Playbooks if someone want's to take the time to QA this.
Adobe is getting away from Flash on mobile devices. But the focused on
AIR on mobile. As you can see in the Matterhorn 2Go app [5] this will
work even on iOS devices.
But if you decide to switch from FLV to H.264 everything is fragmented
and you'll have to have several techniques to serve all the devices.
Rüdiger
On 20.04.2012 15:29, Don Rainwater wrote:
For us, one of the big draws for streaming is mobile devices, and right now
that means tablets that are almost all iPads, and smart phones where the
majority are iPhones. So we need anything that we stream to be compatible with
iOS. HTTP Live Streaming does that natively, so there are benefits to choosing
that for at least as long as the tablet market is an iPad market. (I'm not
bashing Android tablets here. They just haven't gotten much traction in the
market yet.)
Last time I looked (and it has been a while), even the mobile devices that
support Flash don't do it well, and Adobe is moving away from Flash on mobile,
right?
As you said, multiple streaming techniques may be required, at least until the
various streaming options (HDS, HLS, etc.) converge.
On Apr 20, 2012, at 7:56 AM, Ruediger Rolf wrote:
After one week I have to add 2 more findings to my H.264 experiments:
- When rescaling you should be aware that the dimensions of your video must stay even
numbers. If you use the ffmpeg option "-vf scale=200:-1" you might be unlucky
that your hight can get an odd number.
- streaming of h.264 files to mobile devices will require multiple streaming
techniques [4].
And now for me the interesting question would be, who has more experience with
these different streaming techniques:
- RTMP worked very reliable for us for several years now with FLV videos.
Additional to any desktop PC that has Flash installed it works in our Android
and iOS app [5]. Unfortunately it does not work with H.264 on iOS (but on
Android).
- HTTP Dynamic Streaming (HDS) is Adobes approach to http-streaming. I never
used it yet, and again it does not work on iOS. I have not tried it on other
plattforms yet.
- HTTP Live Streaming (HLS) is Apples approach on http-streaming. This now
works for iOS only and the latest Mac OS version. You cannot use it on Windows,
Linux, Android, Mac OS 10.6 (try it yourself [6]). So I'm wondering why such a
bad supported format is currently so highly requested. Does anyone here have
experience with HLS yet?
I'm currently considering to switch back to FLV as everything seemed much
easier with this format.
Regards
Rüdiger
[4] http://forums.adobe.com/message/4100805
[5] http://vm193.rz.uni-osnabrueck.de/matterhorn2go/index_en.html
[6] https://developer.apple.com/resources/http-streaming/examples/
On 16.04.2012 17:05, Ruediger Rolf wrote:
Dear fellow Matterhorn users,
as we start to use our Matterhorn 1.3 in these days, I wanted to improve our
workflow definitions. I decided that I wanted to use H.264 only, as we luckly
updated to a Wowza Media Server [1] that allows us to stream H.264 [2].
So I created some MP4 encoding profiles, updated the multi-quality workflow
definition and created a HD-workflow definition based on multi-quality. These
updates are documented here [3].
In creating the MP4 encodings I recognized that MP4 behaves quite different
from FLV. I don't know how much I like these changes and I must say that FLV
had some great features that I currently miss. So what has to be considered
when encoding MP4:
1. If you want synchronous playback of two streams the two videos for presenter
and presentation need to have the same framerate and GOP structure. If this is
not given the videos can be out of sync for several seconds.
2. The Engage Player can only jump to key-frames. These are usually set every
300 frames. That means every 10s on NTSC, 12s on PAL. If you reduce the
framerate to save bandwith the intervall may become even greater. You can try
to set the key frame interval manually, but the presets may overwrite these
changes. The consequence is that when you jump to a chapter in the Matterhorn
engage player you will not jump to the exact second but to the last keyframe,
that may be several seconds earlier. FLV did not have this problem as the
format somehow stores the reference to the keyframes in the metadata.
3. At least in the engage player there seems to be a problem that the h.264
videos are not always lip sync, which means that the delay of audio and video
is more than 80ms.
4. There are several "profiles" for H.264. I have not understood the
differences between these profiles in depth. The advantage of baseline profile is that it
should run on the most devices and is probably hardware accelerated. So at least one of
you profiles should be a basline profile. From my subjective tests the lip-sync issues is
not that recognizeable on main and high profiles somehow.
5. There are several encoding presets (from ultrafast to veryslow) for x264. There is a dublication
of presets ffmpeg has its own which are called with the "-vpre" option and the presets
from the x264 codec itself which can be called with the "-preset" option. The
vpre-settings create a MP4 that is not playable in Flash, so I recommend to use the x264 presets
that all seem to work fine. In my tests ultrafast was more than 10x faster than veryslow. From my
test-encodings I decided to use the medium setting (2-3x the encoding time of ultrafast), as the
video-quality seemed okay for me than, but I might adjust this with more test videos around. (In
general the baseline profile encoded 30% in my examples than the other profiles).
I hope my findings are helpful to others, as it seemed to me that there was
quite a lot chatting on IRC about using H.264.
Rüdiger
[1] A guide on how to setup Wowza with Matterhorn can be found here:
http://opencast.jira.com/wiki/display/MHDOC/Wowza+Media+Server+3+v1.3
[2] Red5 does not allow seeking in MP4 files somehow.
[3]
http://opencast.jira.com/wiki/display/MH/HD-Video+%28720p%29+with+H.264+encoding+only
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