[x264-devel] Multithread in x264

[Son Minh Tran]

Dear all
I would like to understand more the implementation of multithreading 
coding in x264. I already check some related discussing threads.  But I 
still have some problems to fingure out  your technique as followings:
1.Before revision 607,  each thread  encodes  one slice , whose size (in 
MB) is equal to the frame size  divided by No. of thread . You said  
this method  has penalty on bitrate. Is it due to the independent 
treatment of  slices in the same frame (therefore no spatial corellation 
can be exploited at the boundary of slices)?. There is no synchron at 
all between threads, isn,t it ?
2. From revision 607, you deployed multithread based on frame. It means 
that frame can no longer be devided into more slices (I cannot find any 
parameters for setting the size of slice)? With this method, you have to 
introduce the function x264_frame_cond_wait to ensure the fact that in 
the current Frame B/P encoded by thread X, before encoding a MB, all of 
its probable reference MBs in other frames (therefore encoded by other 
threads)  must be  encoded  and reconstructed (then they can be used as 
references). I  still don't  understand the reason you set 24 to  
X264_THREAD_HEIGHT.
Thank you for your clarification
Son
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