[FFmpeg-devel] [PATCH 1/2] configure: Clearer documentation for "disable-safe-bitstream-reader"

[FFmpeg-devel] [PATCH 1/2] configure: Clearer documentation for "disable-safe-bitstream-reader"

[Michael Niedermayer]

Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>
---
 configure | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/configure b/configure
index 14f7bcde0e2..bdebfc2f6a4 100755
--- a/configure
+++ b/configure
@@ -435,7 +435,8 @@ Advanced options (experts only):
   --enable-hardcoded-tables use hardcoded tables instead of runtime generation
   --disable-safe-bitstream-reader
                            disable buffer boundary checking in bitreaders
-                           (faster, but may crash)
+                           (This disables security checks and can cause undefined behavior,
+                            can cause crashes or worse but may be faster)
   --sws-max-filter-size=N  the max filter size swscale uses [$sws_max_filter_size_default]
 
 Optimization options (experts only):
-- 
2.48.1

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[FFmpeg-devel] [PATCH 2/2] avcodec/ffv1enc: remap prettification and bufixes

[Michael Niedermayer]

Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>
---
 libavcodec/ffv1enc.c | 19 ++++++++++++++-----
 1 file changed, 14 insertions(+), 5 deletions(-)

diff --git a/libavcodec/ffv1enc.c b/libavcodec/ffv1enc.c
index 5b251ac2e80..4340d1b8732 100644
--- a/libavcodec/ffv1enc.c
+++ b/libavcodec/ffv1enc.c
@@ -1275,6 +1275,7 @@ typedef struct RemapEncoderState {
     int i;
     int pixel_num;
     int p;
+    int current_mul_index;
 } RemapEncoderState;
 
 static inline void copy_state(RemapEncoderState *dst, const RemapEncoderState *src)
@@ -1292,6 +1293,7 @@ static inline void copy_state(RemapEncoderState *dst, const RemapEncoderState *s
     dst->i              = src->i;
     dst->pixel_num      = src->pixel_num;
     dst->p              = src->p;
+    dst->current_mul_index = src->current_mul_index;
 }
 
 static inline void encode_mul(RemapEncoderState *s, int mul_index)
@@ -1318,9 +1320,11 @@ static int encode_float32_remap_segment(FFV1SliceContext *sc, Unit unit[4][65536
         s.compact_index = -1;
         s.lu = 0;
         s.run = 0;
+        s.current_mul_index = -1;
     }
 
     for (; s.i < s.pixel_num+1; s.i++) {
+        int current_mul = s.current_mul_index < 0 ? 1 : FFABS(s.mul[s.current_mul_index]);
         int64_t val;
         if (s.i == s.pixel_num) {
             if (s.last_val == 0xFFFFFFFF) {
@@ -1332,8 +1336,6 @@ static int encode_float32_remap_segment(FFV1SliceContext *sc, Unit unit[4][65536
             val = unit[s.p][s.i].val;
 
         if (s.last_val != val) {
-            int current_mul_index = ((s.last_val + 1) * s.mul_count) >> 32;
-            int current_mul = s.i ? FFABS(s.mul[current_mul_index]) : 1;
             int64_t delta = 0;
             av_assert2(s.last_val < val);
             av_assert2(current_mul > 0);
@@ -1349,14 +1351,16 @@ static int encode_float32_remap_segment(FFV1SliceContext *sc, Unit unit[4][65536
             }
             av_assert2(s.last_val < val);
             if (s.lu) {
-                s.index_stack[s.run] = current_mul_index;
+                s.index_stack[s.run] = s.current_mul_index;
                 av_assert2(s.run < FF_ARRAY_ELEMS(s.delta_stack));
                 if (val - s.last_val == 1) {
                     s.delta_stack[s.run] = delta;
                     s.run ++;
+                    av_assert2(s.i == s.pixel_num || s.last_val + current_mul + delta == unit[s.p][s.i].val);
                     s.last_val += current_mul + delta;
                 } else {
                     put_symbol_inline(&s.rc, s.state[s.lu][0], s.run, 0, NULL, NULL);
+
                     for(int k=0; k<s.run; k++) {
                         int stack_mul = s.mul[ s.index_stack[k] ];
                         if (stack_mul>1)
@@ -1373,14 +1377,19 @@ static int encode_float32_remap_segment(FFV1SliceContext *sc, Unit unit[4][65536
             } else {
                 av_assert2(s.run == 0);
                 put_symbol_inline(&s.rc, s.state[s.lu][0], val - s.last_val - 1, 0, NULL, NULL);
+
                 if (current_mul > 1)
                     put_symbol_inline(&s.rc, s.state[s.lu][1], delta, 1, NULL, NULL);
                 if (val - s.last_val == 1)
                     s.lu ^= 1;
-                s.last_val += (val - s.last_val) * current_mul + delta;
 
-                encode_mul(&s, ((s.last_val + 1) * s.mul_count) >> 32);
+                av_assert2(s.i == s.pixel_num || s.last_val + (val - s.last_val) * current_mul + delta == unit[s.p][s.i].val);
+                if (s.i < s.pixel_num)
+                    s.last_val = unit[s.p][s.i].val;
             }
+            s.current_mul_index = ((s.last_val + 1) * s.mul_count) >> 32;
+            if (!s.run)
+                encode_mul(&s, s.current_mul_index);
             s.compact_index ++;
         }
         if (final && s.i < s.pixel_num)
-- 
2.48.1

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