pthreads: drop has_b_frames mangling, its buggy in many many ways,

not to mention race conditions and that its used for stream copy, used to determine IPB type by
applications and other things.
Fixes various frame drop/timestamp issues with frame multithreading.

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

libavcodec/pthread.c

@@ -364,7 +364,6 @@ static int update_context_from_thread(AVCodecContext *dst, AVCodecContext *src,
 
     if (for_user) {
         dst->coded_frame   = src->coded_frame;
-        dst->has_b_frames += src->thread_count - 1;
     } else {
         if (dst->codec->update_thread_context)
             err = dst->codec->update_thread_context(dst, src);
@@ -686,7 +685,6 @@ static void frame_thread_free(AVCodecContext *avctx, int thread_count)
     av_freep(&fctx->threads);
     pthread_mutex_destroy(&fctx->buffer_mutex);
     av_freep(&avctx->thread_opaque);
-    avctx->has_b_frames -= avctx->thread_count - 1;
 }
 
 static int frame_thread_init(AVCodecContext *avctx)

libavformat/utils.c

@@ -1004,11 +1004,6 @@ static void compute_pkt_fields(AVFormatContext *s, AVStream *st,
     delay= st->codec->has_b_frames;
     presentation_delayed = 0;
 
-    // ignore delay caused by frame threading so that the mpeg2-without-dts
-    // warning will not trigger
-    if (delay && st->codec->active_thread_type&FF_THREAD_FRAME)
-        delay -= st->codec->thread_count-1;
-
     /* XXX: need has_b_frame, but cannot get it if the codec is
         not initialized */
     if (delay &&