Wowza: Modifying a Stream as it is playing? - wowza

Question

It seems like this must be happening in many different contexts such as adding subtitles. What I want to do is grab a frame, change some feature within it and then "put it back" so that the end user sees this change. I think I know how to grab and modify the frame but re-inserting it into the stream I do not see how to do. Would appreciate a link or code.

Answer 1

On a live stream, there are a few things to consider depending on what the end goal might be. If it's true packet / frame level manipulation you would likely need to make the modification and set the output to a new stream (source remains unscathed but new stream has the modification). Modifying the stream inline will be very problematic.
Packet level modification using IMediaStreamLivePacketNotify
You can implement the IMediaStreamLivePacketNotify interface to handle new packets and modify them as necessary. Example implementation:
private class PacketListener implements IMediaStreamLivePacketNotify
{
#Override
public void onLivePacket(IMediaStream stream, AMFPacket packet)
{
// handle packet modifications
}
}
Upon modifying the packet you could publish it to a secondary stream that you publish through the Publisher object.
Publisher.createInstance(vhost, appName, appInstName);
The publisher contains functionality to add A/V data to your new stream:
switch (packet.getType())
{
case IVHost.CONTENTTYPE_AUDIO:
publisher.addAudioData(packet.getData(), packet.getAbsTimecode());
break;
case IVHost.CONTENTTYPE_VIDEO:
publisher.addVideoData(packet.getData(), packet.getAbsTimecode());
break;
case IVHost.CONTENTTYPE_DATA:
case IVHost.CONTENTTYPE_DATA3:
publisher.addDataData(packet.getData(), packet.getAbsTimecode());
}
There is similar functionality within the Duplicate Streams module for a broader look at this implementation.
Packet level modification using getPlayPackets()
You could also look at the IMediaStream object and leverage the IMediaStream.getPlayPackets() functionality. Then you can obtain the packets and modify as needed in a corresponding thread that continually processes the inbound stream. Thereafter, you could use the Publisher object to publish the new stream (similar to the above).
Metadata injection
However, if you are just looking to inject some metadata the process becomes much more basic. You can modify the AMFDataList within the source stream to include the new meta information.
Adding onto the stream
If you are looking to add data onto the inline stream (vs modifying it) you could simply add it via the ImediaStream object:
IMediaStream.addAudioData(..)