Måns Rullgård <[email protected]> writes:
> Måns Rullgård <[email protected]> writes:
>
>> "Ronald S. Bultje" <[email protected]> writes:
>>
>>> Prevent values in floor1[] from wrapping over uint16_t boundaries (in
>>> crafted bitstreams, they can go < 0), which causes them to wrap to
>>> MAXUINT16, causing huge jumps in the dB LUT indexes. Likewise, clip
>>> (rather than wrap) dB LUT indexes, to prevent jumping of indexes at
>>> uint8_t wrapping boundaries.
>>> ---
>>> libavcodec/vorbis.c | 16 ++++++++--------
>>> libavcodec/vorbisdec.c | 10 +++++-----
>>> 2 files changed, 13 insertions(+), 13 deletions(-)
>>>
>
> [...]
>
>> This is pointless. The value passed into these functions is a uint8_t.
>> To get the effect you're looking for, you need to clip the value
>> computed in ff_vorbis_floor1_render_list().
>
> To be clear, this patch should be enough:
>
> diff --git a/libavcodec/vorbis.c b/libavcodec/vorbis.c
> index 0b26870..7d6a4f0 100644
> --- a/libavcodec/vorbis.c
> +++ b/libavcodec/vorbis.c
> @@ -207,9 +207,9 @@ void ff_vorbis_floor1_render_list(vorbis_floor1_entry *
> list, int values,
> int multiplier, float *out, int samples)
> {
> int lx, i;
> - uint8_t ly;
> + int ly;
> lx = 0;
> - ly = y_list[0] * multiplier;
> + ly = av_clip_uint8(y_list[0] * multiplier);
> for (i = 1; i < values; i++) {
> int pos = list[i].sort;
> if (flag[pos]) {
I missed the second place ly is assigned in the loop. This should do it:
diff --git a/libavcodec/vorbis.c b/libavcodec/vorbis.c
index 0b26870..a0f1090 100644
--- a/libavcodec/vorbis.c
+++ b/libavcodec/vorbis.c
@@ -206,10 +206,9 @@ void ff_vorbis_floor1_render_list(vorbis_floor1_entry *
list, int values,
uint16_t *y_list, int *flag,
int multiplier, float *out, int samples)
{
- int lx, i;
- uint8_t ly;
+ int lx, ly, i;
lx = 0;
- ly = y_list[0] * multiplier;
+ ly = av_clip_uint8(y_list[0] * multiplier);
for (i = 1; i < values; i++) {
int pos = list[i].sort;
if (flag[pos]) {
@@ -218,7 +217,7 @@ void ff_vorbis_floor1_render_list(vorbis_floor1_entry *
list, int values,
if (lx < samples)
render_line(lx, ly, FFMIN(x1,samples), y1, out);
lx = x1;
- ly = y1;
+ ly = av_clip_uint8(y1);
}
if (lx >= samples)
break;
--
Måns Rullgård
[email protected]
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