Memory corruption via unchecked stream count

Stack buffer overflow in the MPEG-PS muxer in FFmpeg before commit 9d786e4 allows attackers to corrupt memory via high-stream-count input. In libavformat/mpegenc.c, the muxer uses a fixed-size stack buffer for per-stream bookkeeping and writes past that buffer when the number of streams exceeds the buffer's capacity. Reachability requires attacker-controlled media to be processed in an MPEG-PS muxing workflow, so the practical result is a crash or broader memory corruption in the calling process rather than a directly reachable network flaw.