[FFmpeg-devel] [PATCH 3/9] avcodec/sanm: disable left/top for fullscreen codecs

[Manuel Lauss <manuel.lauss@gmail.com>]

The block-based codecs 37/47/48 work on the full frame, and there's no
existing LucasArts game video that uses left/top offsets for these,
as it doesn't make sense. Ignore the left/top parameters for these codecs.

Signed-off-by: Manuel Lauss <manuel.lauss@gmail.com>
---
Well, except for SotE, which uses "top" to move the widescreen video
to the center of the 4:3 game window, but ffmpeg doesn't need do do
that.

 libavcodec/sanm.c | 40 +++++++++++++++++++++++-----------------
 1 file changed, 23 insertions(+), 17 deletions(-)

diff --git a/libavcodec/sanm.c b/libavcodec/sanm.c
index ca345bc61a..b2923515b1 100644
--- a/libavcodec/sanm.c
+++ b/libavcodec/sanm.c
@@ -621,8 +621,7 @@ static inline void codec37_mv(uint8_t *dst, const uint8_t *src,
     }
 }
 
-static int old_codec37(SANMVideoContext *ctx, int top,
-                       int left, int width, int height)
+static int old_codec37(SANMVideoContext *ctx, int width, int height)
 {
     int i, j, k, l, t, run, len, code, skip, mx, my;
     ptrdiff_t stride = ctx->pitch;
@@ -638,8 +637,8 @@ static int old_codec37(SANMVideoContext *ctx, int top,
     flags = bytestream2_get_byte(&ctx->gb);
     bytestream2_skip(&ctx->gb, 3);
 
-    if (decoded_size > ctx->height * stride - left - top * stride) {
-        decoded_size = ctx->height * stride - left - top * stride;
+    if (decoded_size > ctx->height * stride) {
+        decoded_size = ctx->height * stride;
         av_log(ctx->avctx, AV_LOG_WARNING, "Decoded size is too large.\n");
     }
 
@@ -649,8 +648,8 @@ static int old_codec37(SANMVideoContext *ctx, int top,
         FFSWAP(uint16_t*, ctx->frm1, ctx->frm2);
     }
 
-    dst  = ((uint8_t*)ctx->frm1) + left + top * stride;
-    prev = ((uint8_t*)ctx->frm2) + left + top * stride;
+    dst  = ((uint8_t*)ctx->frm1);
+    prev = ((uint8_t*)ctx->frm2);
 
     if (mvoff > 2) {
         av_log(ctx->avctx, AV_LOG_ERROR, "Invalid motion base value %d.\n", mvoff);
@@ -923,15 +922,14 @@ static void codec47_comp1(SANMVideoContext *ctx, uint8_t *dst_in, int width,
     }
 }
 
-static int old_codec47(SANMVideoContext *ctx, int top,
-                       int left, int width, int height)
+static int old_codec47(SANMVideoContext *ctx, int width, int height)
 {
     uint32_t decoded_size;
     int i, j;
     ptrdiff_t stride = ctx->pitch;
-    uint8_t *dst   = (uint8_t *)ctx->frm0 + left + top * stride;
-    uint8_t *prev1 = (uint8_t *)ctx->frm1 + left + top * stride;
-    uint8_t *prev2 = (uint8_t *)ctx->frm2 + left + top * stride;
+    uint8_t *dst   = (uint8_t *)ctx->frm0;
+    uint8_t *prev1 = (uint8_t *)ctx->frm1;
+    uint8_t *prev2 = (uint8_t *)ctx->frm2;
     uint8_t auxcol[2];
     int tbl_pos = bytestream2_tell(&ctx->gb);
     int seq     = bytestream2_get_le16(&ctx->gb);
@@ -945,8 +943,8 @@ static int old_codec47(SANMVideoContext *ctx, int top,
     decoded_size = bytestream2_get_le32(&ctx->gb);
     bytestream2_skip(&ctx->gb, 8);
 
-    if (decoded_size > ctx->height * stride - left - top * stride) {
-        decoded_size = ctx->height * stride - left - top * stride;
+    if (decoded_size > ctx->height * stride) {
+        decoded_size = ctx->height * stride;
         av_log(ctx->avctx, AV_LOG_WARNING, "Decoded size is too large.\n");
     }
 
@@ -957,8 +955,8 @@ static int old_codec47(SANMVideoContext *ctx, int top,
     }
     if (!seq) {
         ctx->prev_seq = -1;
-        memset(prev1, auxcol[0], (ctx->height - top) * stride);
-        memset(prev2, auxcol[1], (ctx->height - top) * stride);
+        memset(prev1, auxcol[0], ctx->height * stride);
+        memset(prev2, auxcol[1], ctx->height * stride);
     }
 
     switch (compr) {
@@ -1289,6 +1287,14 @@ static int process_frame_obj(SANMVideoContext *ctx)
             av_log(ctx->avctx, AV_LOG_WARNING, "resizing too large fobj.\n");
         }
     }
+
+    if (codec == 37 || codec == 47 || codec == 48) {
+        /* these codecs work on full frames.  In SotE only, "top" is used
+         * to create a black bar at the top to center the  video inside
+         * the 640x480 game window.  We don't need/want that here.
+         */
+        left = top = 0;
+    }
     bytestream2_skip(&ctx->gb, 4);
 
     switch (codec) {
@@ -1296,9 +1302,9 @@ static int process_frame_obj(SANMVideoContext *ctx)
     case 3:
         return old_codec1(ctx, top, left, w, h);
     case 37:
-        return old_codec37(ctx, top, left, w, h);
+        return old_codec37(ctx, w, h);
     case 47:
-        return old_codec47(ctx, top, left, w, h);
+        return old_codec47(ctx, w, h);
     case 48:
         return old_codec48(ctx, w, h);
     default:
-- 
2.48.1

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