[FFmpeg-devel] MAX_THREADS for ffmpeg-mt mp4

[Frank Barchard]

This change benefits ffmpeg-mt for mp4.
With the old value, you were limited to 8 threads, and a crash would
occur if you set more than 10.

Here is a benchmark (chromium media_bench) of number of threads on an
8 core / 16 thread Nehalem.
It shows performance continues to improve beyond 8 threads.

Threads vs Time/Frame (ms)
1 ? 13.14
2 ?   7.31
3 ?   5.73
4 ?   4.07
5 ?   4.50
6 ?   3.82
7 ?   3.21
8 ?   2.93
9 ?   2.62
10 ? 2.40
11 ? 2.19
12 ? 2.03
13 ? 1.92
14 ? 1.83
15 ? 1.76
16 ? 1.70

Index: libavcodec/mpegvideo.h
===================================================================
--- libavcodec/mpegvideo.h ? ? ?(revision 20006)
+++ libavcodec/mpegvideo.h ? ? ?(working copy)
@@ -54,7 +54,7 @@
?#define MAX_FCODE 7
?#define MAX_MV 2048
-#define MAX_THREADS 8
+#define MAX_THREADS 16
?#define MAX_PICTURE_COUNT 32