On 01/01/2017 10:07 AM, Victor dMdB wrote:
On Sun, 1 Jan 2017, at 11:04 PM, Charles wrote:
On 01/01/2017 05:22 AM, Victor dMdB wrote:
If I have multiple streams of distinct data, how would I go about making
sure data is thread safe in real-time applications?
My code is in C++, so I managed to pass a write function using extern C
but that makes the function global (ie not thread safe), I tried fixing
with thread_local but i then ran into other issues.
I then tried using the private data ptr, but then I get a data race,
because I was just polling with a while loop in another thread, which is
rather unreliable.
Are there any previous examples of how to do this?
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Muxing or Demuxing? Multiple streams are files or actual transport
streams?
Thanks
Charles
In my case it is to mux mp4 files into rtp format, would it be different
if it were transport streams?
It could change they way you want to tackle it.
First, to make it thread safe you have to use some form of synchronization.
I use a template LockingQueue.hpp
Code :
public :
void PushItem( T f_ )
{
std::lock_guard<std::mutex> lock(m_queue_mtx);
m_queue.push( f_ );
}
T PopItem()
{
T f_;
std::lock_guard<std::mutex> lock(m_queue_mtx);
f_ = m_queue.front();
m_queue.pop();
return f_;
}
protected :
std::queue<T> m_queue;
std::mutex m_queue_mtx;
You can google thread safe multiple producers and there are lots of different
ways to implement.
Run the stream out as a thread and give it a SendPacket( AvPacket * in_pkt )
method that will PushItem( in_pkt )
NOTE : You may need to do a memcpy depending on how the packets are allocated. Do memcpy before PushItem/SendPacket to prevent additional
lock time
In the while loop in the thread check the queue Size() and next_pkt = PopItem()
Then do any ts scaling and stream re-ident and av_interleaved_write_frame(
m_av_out_fmt_ctx, next_pkt );
If the input is already in transport streams, then you could just round robin
the input sockets and just forward each packet as it comes in.
Thanks
Charles
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