Rename some variables and add some comments to try to be a bit more clear.

Originally committed as revision 15510 to svn://svn.ffmpeg.org/ffmpeg/trunk

libavcodec/indeo3.c

@@ -202,7 +202,7 @@ typedef struct {
 
 static void iv_Decode_Chunk(Indeo3DecodeContext *s,
         uint8_t *cur, uint8_t *ref, int width, int height,
-        const uint8_t *buf1, long fflags2, const uint8_t *hdr,
+        const uint8_t *buf1, long cb_offset, const uint8_t *hdr,
         const uint8_t *buf2, int min_width_160)
 {
     uint8_t bit_buf;
@@ -314,7 +314,7 @@ static void iv_Decode_Chunk(Indeo3DecodeContext *s,
             k = *buf1 >> 4;
             j = *buf1 & 0x0f;
             buf1++;
-            lv = j + fflags2;
+            lv = j + cb_offset;
 
             if((lv - 8) <= 7 && (k == 0 || k == 3 || k == 10)) {
                 cp2 = s->ModPred + ((lv - 8) << 7);
@@ -326,10 +326,10 @@ static void iv_Decode_Chunk(Indeo3DecodeContext *s,
             }
 
             if(k == 1 || k == 4) {
-                lv = (hdr[j] & 0xf) + fflags2;
+                lv = (hdr[j] & 0xf) + cb_offset;
                 correction_type_sp[0] = s->corrector_type + (lv << 8);
                 correction_lp[0] = correction + (lv << 8);
-                lv = (hdr[j] >> 4) + fflags2;
+                lv = (hdr[j] >> 4) + cb_offset;
                 correction_lp[1] = correction + (lv << 8);
                 correction_type_sp[1] = s->corrector_type + (lv << 8);
             } else {
@@ -973,34 +973,35 @@ static av_cold int indeo3_decode_init(AVCodecContext *avctx)
 static unsigned long iv_decode_frame(Indeo3DecodeContext *s,
                                      const uint8_t *buf, int buf_size)
 {
-    unsigned int hdr_width, hdr_height,
+    unsigned int image_width, image_height,
                  chroma_width, chroma_height;
-    unsigned long fflags1, fflags2, fflags3, offs1, offs2, offs3, offs;
+    unsigned long flags, cb_offset, data_size,
+                  y_offset, v_offset, u_offset, mc_vector_count;
     const uint8_t *hdr_pos, *buf_pos;
 
     buf_pos = buf;
-    buf_pos += 18;
+    buf_pos += 18; /* skip OS header (16 bytes) and version number */
 
-    fflags1 = bytestream_get_le16(&buf_pos);
-    fflags3 = bytestream_get_le32(&buf_pos);
-    fflags2 = *buf_pos++;
-    buf_pos += 3;
-    hdr_height = bytestream_get_le16(&buf_pos);
-    hdr_width  = bytestream_get_le16(&buf_pos);
+    flags = bytestream_get_le16(&buf_pos);
+    data_size = bytestream_get_le32(&buf_pos);
+    cb_offset = *buf_pos++;
+    buf_pos += 3; /* skip reserved byte and checksum */
+    image_height = bytestream_get_le16(&buf_pos);
+    image_width  = bytestream_get_le16(&buf_pos);
 
-    if(avcodec_check_dimensions(NULL, hdr_width, hdr_height))
+    if(avcodec_check_dimensions(NULL, image_width, image_height))
         return -1;
 
-    chroma_height = ((hdr_height >> 2) + 3) & 0x7ffc;
-    chroma_width = ((hdr_width >> 2) + 3) & 0x7ffc;
-    offs1 = bytestream_get_le32(&buf_pos);
-    offs2 = bytestream_get_le32(&buf_pos);
-    offs3 = bytestream_get_le32(&buf_pos);
-    buf_pos += 4;
+    chroma_height = ((image_height >> 2) + 3) & 0x7ffc;
+    chroma_width = ((image_width >> 2) + 3) & 0x7ffc;
+    y_offset = bytestream_get_le32(&buf_pos);
+    v_offset = bytestream_get_le32(&buf_pos);
+    u_offset = bytestream_get_le32(&buf_pos);
+    buf_pos += 4; /* reserved */
     hdr_pos = buf_pos;
-    if(fflags3 == 0x80) return 4;
+    if(data_size == 0x80) return 4;
 
-    if(fflags1 & 0x200) {
+    if(flags & 0x200) {
         s->cur_frame = s->iv_frame + 1;
         s->ref_frame = s->iv_frame;
     } else {
@@ -1008,28 +1009,28 @@ static unsigned long iv_decode_frame(Indeo3DecodeContext *s,
         s->ref_frame = s->iv_frame + 1;
     }
 
-    buf_pos = buf + 16 + offs1;
-    offs = bytestream_get_le32(&buf_pos);
+    buf_pos = buf + 16 + y_offset;
+    mc_vector_count = bytestream_get_le32(&buf_pos);
 
-    iv_Decode_Chunk(s, s->cur_frame->Ybuf, s->ref_frame->Ybuf, hdr_width,
-                    hdr_height, buf_pos + offs * 2, fflags2, hdr_pos, buf_pos,
-                    FFMIN(hdr_width, 160));
+    iv_Decode_Chunk(s, s->cur_frame->Ybuf, s->ref_frame->Ybuf, image_width,
+                    image_height, buf_pos + mc_vector_count * 2, cb_offset, hdr_pos, buf_pos,
+                    FFMIN(image_width, 160));
 
     if (!(s->avctx->flags & CODEC_FLAG_GRAY))
     {
 
-        buf_pos = buf + 16 + offs2;
-        offs = bytestream_get_le32(&buf_pos);
+        buf_pos = buf + 16 + v_offset;
+        mc_vector_count = bytestream_get_le32(&buf_pos);
 
         iv_Decode_Chunk(s, s->cur_frame->Vbuf, s->ref_frame->Vbuf, chroma_width,
-                chroma_height, buf_pos + offs * 2, fflags2, hdr_pos, buf_pos,
+                chroma_height, buf_pos + mc_vector_count * 2, cb_offset, hdr_pos, buf_pos,
                 FFMIN(chroma_width, 40));
 
-        buf_pos = buf + 16 + offs3;
-        offs = bytestream_get_le32(&buf_pos);
+        buf_pos = buf + 16 + u_offset;
+        mc_vector_count = bytestream_get_le32(&buf_pos);
 
         iv_Decode_Chunk(s, s->cur_frame->Ubuf, s->ref_frame->Ubuf, chroma_width,
-                chroma_height, buf_pos + offs * 2, fflags2, hdr_pos, buf_pos,
+                chroma_height, buf_pos + mc_vector_count * 2, cb_offset, hdr_pos, buf_pos,
                 FFMIN(chroma_width, 40));
 
     }