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IBroadcastStream.saveAs and a less than perfect connection Options · View
jwhitley
Posted: Friday, April 13, 2012 2:17:53 PM
Rank: Apprentice Coder
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Joined: 8/14/2011
Posts: 48
Points: 138
Hi All,

A major part of my apps functionality is the ability for users to record a video / audio stream for later sharing. If their connection to the server is good then all appears well, but if this connection is "weak" (although the netconnection does not drop), then the video might well corrupt after just a few seconds, rendering it useless.

This might be a weakness in the .flv format, but if that is the case, and knowing that I cannot guarantee the quality of the client > server connection, what steps can I take to ensure video plays correctly? Stuttering video is fine. Corrupt video is not.

WebOrbFor.Net v 4.5 on .Net framework 4, Win2K8R2

Many thanks.
Cyril
Posted: Monday, April 16, 2012 1:49:32 PM
Rank: Administration
Groups: Administration , Member

Joined: 9/10/2009
Posts: 320
Points: 778
Location: US
jwhitley wrote:
Hi All,

A major part of my apps functionality is the ability for users to record a video / audio stream for later sharing. If their connection to the server is good then all appears well, but if this connection is "weak" (although the netconnection does not drop), then the video might well corrupt after just a few seconds, rendering it useless.

This might be a weakness in the .flv format, but if that is the case, and knowing that I cannot guarantee the quality of the client > server connection, what steps can I take to ensure video plays correctly? Stuttering video is fine. Corrupt video is not.

WebOrbFor.Net v 4.5 on .Net framework 4, Win2K8R2

Many thanks.


There are few questions so far.
First of all, what kind of exception/event you get when "the video might well corrupt after just a few seconds".
Next, what do you mean by words "rendering it useless" ?
What do you mean by words "This might be a weakness in the .flv format" ? What kind of weaknesses are there?

"what steps can I take to ensure video plays correctly". Steps are described in the adobe API well and I believe there is nothing else that you can do. Just follow the API and you will be fine. I am not sure if WebORB related to your question anyhow, but anyway, I am looking forward to get more details regarding to my questions above




jwhitley
Posted: Tuesday, April 17, 2012 4:39:45 AM
Rank: Apprentice Coder
Groups: Member

Joined: 8/14/2011
Posts: 48
Points: 138
Cyril wrote:
There are few questions so far.
First of all, what kind of exception/event you get when "the video might well corrupt after just a few seconds".
Next, what do you mean by words "rendering it useless" ?
What do you mean by words "This might be a weakness in the .flv format" ? What kind of weaknesses are there?

"what steps can I take to ensure video plays correctly". Steps are described in the adobe API well and I believe there is nothing else that you can do. Just follow the API and you will be fine. I am not sure if WebORB related to your question anyhow, but anyway, I am looking forward to get more details regarding to my questions above


Hi Cyril,

To answer your questions in order:

1.) No exception, but the video freezes in every commercial .flv player I try (and I've tried several) after a few seconds. WebOrb might create a 50mB .flv file which show a length of 58 minutes but stops playing after 3-4 seconds.

2.) By rendering it useless, I mean that I know there are "good" video frames available for playback after the corruption, but you cannot play them. I have not tried re-streaming the files. perhaps I'll give this a go.

3.) I dont know of any specific flaw in the .flv format, but flv players seem incapable of continuing playback after a corruption.

I've not narrowed down this issue to being connection specific. I have an incling it might be happening when multiple streams are recording at the same time. I've also noticed that frame rates / resolution can change midway through a recorded file (is this down to adaptive bitrate of the source stream?). Perhaps this is part of the issue?

I have watched a stream while it is being recorded server side. I have seen stutters in the "live" stream, but the stream continues OK, but the recorded .flv fails at the point of the stutter.

I'll try and get more specific info as to when this happens.

Many thanks.
jwhitley
Posted: Thursday, June 14, 2012 4:49:41 PM
Rank: Apprentice Coder
Groups: Member

Joined: 8/14/2011
Posts: 48
Points: 138
Apologies for the delay in replying. It has taken me a while to narrow down what is happening, but...

The recording problem happens on second and subsequent recording events from the same client connection. My app allows users to record short videos. If the user has already used their webcam within the app, the recording corrupts (and is unplayable) at the point the keyframe is sent.

In other words... if I create a new NetConnection object, create a new NetStream upon successful connection and then attach a Camera to the stream, the serverside record will work fine the first time.

Subsequent attempts to use serverside record always corrupt the recorded video file at the point a keyframe is sent. I am guessing the keyframe is the issue, as the point of corruption can be moved from almost immediate to up to 4 seconds into the video by changing the frequency of the keyframe being sent. ie, at 12fps and keyframe interval set to 48, the file corrupts at about 4 seconds. At 12fps and keyframe interval set to 12 the file corrupts at about 1 second.

Using new netconnections, new netstreams, reinitialising the camera etc etc all seem to make no difference. The first recorded file is almost always fine, all subsequent files are almost always corrupt.

Thanks.
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