theora dev - Jan 2008 - ogg packets get lost

Hi,

I am actually working on a c++ wrapper for ogg/theora. It will be a small 
library to easily create command line tools to cut/cat video-files and to 
extract and join the video and audio stream etc.

However, I started the project and found some very strange behaviors:
I stored some ogg_packet objects (which are created on the heap) in a list.
When I make several calls to ogg_stream_pagein() and ogg_stream_packetout(), 
the packets are accidentally overwritten by some nonsense.

I am not sure what really happens, but I guess the libogg writers wanted to 
reduce the memory copy to a minimum, so that there are pointers (packet), 
which will be reused or whatever.

My question is: how do you (other developers) solve this problem? Creating a 
copy of the ogg_packet (including the areas, where the packet pointer directs 
to) would be a way. However I think I have to do the same for the ogg_pages!? 
Or are there any other, easier tricks to solve this problem?

Thanks in advance
Yorn

PS: I added the demo file, I created to figure out the problem

 
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Yorn wrote:
> However, I started the project and found some very strange behaviors:
> I stored some ogg_packet objects (which are created on the heap) in a list.
> When I make several calls to ogg_stream_pagein() and
ogg_stream_packetout(),
> the packets are accidentally overwritten by some nonsense.
IANAGuru, but it sounds as though you are trying to 'keep' the ogg 
packet pointer you get from ogg_stream_packetout(). This is not possible 
- it is only a pointer to data inside the stream, and will most likely 
be invalidated as soon as you add another page into the stream.

The code in player_example.c correctly handles packets before touching 
the stream again.

This was certainly I problem I encountered getting a decoder working - I 
hope this helps!

- Patrick Byrne

Hi Ralph,

thanks for the clarification. 

I think I really have to study the ogg sourcecode, not only the API to 
understand the behavior.

Yorn