avcodec/mpegvideo: support disabling motion compensation

This allows analyzing videos without having prior and current frames mixed
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

libavcodec/avcodec.h

@@ -2587,6 +2587,7 @@ typedef struct AVCodecContext {
 #endif
 #define FF_DEBUG_BUFFERS     0x00008000
 #define FF_DEBUG_THREADS     0x00010000
+#define FF_DEBUG_NOMC        0x01000000
 
 #if FF_API_DEBUG_MV
     /**

libavcodec/mpegvideo.c

@@ -340,6 +340,18 @@ static void mpeg_er_decode_mb(void *opaque, int ref, int mv_dir, int mv_type,
     ff_MPV_decode_mb(s, s->block);
 }
 
+static void gray16(uint8_t *dst, uint8_t *src, int linesize, int h)
+{
+    while(h--)
+        memset(dst + h*linesize, 128, 16);
+}
+
+static void gray8(uint8_t *dst, uint8_t *src, int linesize, int h)
+{
+    while(h--)
+        memset(dst + h*linesize, 128, 8);
+}
+
 /* init common dct for both encoder and decoder */
 av_cold int ff_dct_common_init(MpegEncContext *s)
 {
@@ -348,6 +360,19 @@ av_cold int ff_dct_common_init(MpegEncContext *s)
     ff_hpeldsp_init(&s->hdsp, s->avctx->flags);
     ff_videodsp_init(&s->vdsp, s->avctx->bits_per_raw_sample);
 
+    if (s->avctx->debug & FF_DEBUG_NOMC) {
+        int i;
+        for (i=0; i<4; i++) {
+            s->hdsp.avg_pixels_tab[0][i] = gray16;
+            s->hdsp.put_pixels_tab[0][i] = gray16;
+            s->hdsp.put_no_rnd_pixels_tab[0][i] = gray16;
+
+            s->hdsp.avg_pixels_tab[1][i] = gray8;
+            s->hdsp.put_pixels_tab[1][i] = gray8;
+            s->hdsp.put_no_rnd_pixels_tab[1][i] = gray8;
+        }
+    }
+
     s->dct_unquantize_h263_intra = dct_unquantize_h263_intra_c;
     s->dct_unquantize_h263_inter = dct_unquantize_h263_inter_c;
     s->dct_unquantize_mpeg1_intra = dct_unquantize_mpeg1_intra_c;
@@ -1656,6 +1681,22 @@ int ff_find_unused_picture(MpegEncContext *s, int shared)
     return ret;
 }
 
+static void gray_frame(AVFrame *frame)
+{
+    int i, h_chroma_shift, v_chroma_shift;
+
+    av_pix_fmt_get_chroma_sub_sample(frame->format, &h_chroma_shift, &v_chroma_shift);
+
+    for(i=0; i<frame->height; i++)
+        memset(frame->data[0] + frame->linesize[0]*i, 0x80, frame->width);
+    for(i=0; i<FF_CEIL_RSHIFT(frame->height, v_chroma_shift); i++) {
+        memset(frame->data[1] + frame->linesize[1]*i,
+               0x80, FF_CEIL_RSHIFT(frame->width, h_chroma_shift));
+        memset(frame->data[2] + frame->linesize[2]*i,
+               0x80, FF_CEIL_RSHIFT(frame->width, h_chroma_shift));
+    }
+}
+
 /**
  * generic function called after decoding
  * the header and before a frame is decoded.
@@ -1882,6 +1923,10 @@ int ff_MPV_frame_start(MpegEncContext *s, AVCodecContext *avctx)
         s->dct_unquantize_inter = s->dct_unquantize_mpeg1_inter;
     }
 
+    if (s->avctx->debug & FF_DEBUG_NOMC) {
+        gray_frame(s->current_picture_ptr->f);
+    }
+
     return 0;
 }
 

libavcodec/options_table.h

@@ -248,6 +248,7 @@ static const AVOption avcodec_options[] = {
 {"vis_mb_type", "visualize block types", 0, AV_OPT_TYPE_CONST, {.i64 = FF_DEBUG_VIS_MB_TYPE }, INT_MIN, INT_MAX, V|D, "debug"},
 {"buffers", "picture buffer allocations", 0, AV_OPT_TYPE_CONST, {.i64 = FF_DEBUG_BUFFERS }, INT_MIN, INT_MAX, V|D, "debug"},
 {"thread_ops", "threading operations", 0, AV_OPT_TYPE_CONST, {.i64 = FF_DEBUG_THREADS }, INT_MIN, INT_MAX, V|A|D, "debug"},
+{"nomc", "skip motion compensation", 0, AV_OPT_TYPE_CONST, {.i64 = FF_DEBUG_NOMC }, INT_MIN, INT_MAX, V|A|D, "debug"},
 {"vismv", "visualize motion vectors (MVs)", OFFSET(debug_mv), AV_OPT_TYPE_INT, {.i64 = DEFAULT }, 0, INT_MAX, V|D, "debug_mv"},
 {"pf", "forward predicted MVs of P-frames", 0, AV_OPT_TYPE_CONST, {.i64 = FF_DEBUG_VIS_MV_P_FOR }, INT_MIN, INT_MAX, V|D, "debug_mv"},
 {"bf", "forward predicted MVs of B-frames", 0, AV_OPT_TYPE_CONST, {.i64 = FF_DEBUG_VIS_MV_B_FOR }, INT_MIN, INT_MAX, V|D, "debug_mv"},