On 2021-12-27 05:21 am, Michael Niedermayer wrote:
On Sun, Dec 26, 2021 at 09:30:44PM +0530, Gyan Doshi wrote:
Very high stts sample deltas may occasionally be intended but usually
they are written in error or used to store a negative value for dts correction
when treated as signed 32-bit integers.
This option lets the user set an upper limit, beyond which the delta is clamped
to 1.
Values greater than the limit if negative when cast to int32 are used to adjust
onward dts.
Unit is the track time scale. Default is UINT_MAX - 48000*10 which
allows upto a 10 second dts correction for 48 kHz audio streams while
accommodating 99.9% of uint32 range.
---
v3 changes:
factored out loop
simplified correction logic
this looks more sane now
i guess this cannot be easily split into a seperate patch ?
No, all stts corrections depend on context of earlier corrections.
[...]
@@ -2965,11 +2967,34 @@ static int mov_read_stts(MOVContext *c, AVIOContext
*pb, MOVAtom atom)
sc->stts_data[i].count= sample_count;
sc->stts_data[i].duration= sample_duration;
- av_log(c->fc, AV_LOG_TRACE, "sample_count=%d, sample_duration=%d\n",
+ av_log(c->fc, AV_LOG_TRACE, "sample_count=%u, sample_duration=%u\n",
sample_count, sample_duration);
- duration+=(int64_t)sample_duration*(uint64_t)sample_count;
- total_sample_count+=sample_count;
+ /* STTS sample offsets are uint32 but some files store it as int32
+ * with negative values used to correct DTS delays.
+ There may be abnormally large values as well. */
+ if (sample_duration > c->max_stts_delta) {
+ // assume high delta is a correction if negative when cast as int32
+ int32_t delta_magnitude = (int32_t)sample_duration;
+ av_log(c->fc, AV_LOG_WARNING, "Too large sample offset %u in stts entry
%u with count %u in st:%d. Clipping to 1.\n",
+ sample_duration, i, sample_count, st->index);
+ sc->stts_data[i].duration = 1;
+ corrected_dts += (delta_magnitude < 0 ? (int64_t)delta_magnitude :
1) * sample_count;
+ } else {
+ corrected_dts += sample_duration * sample_count;
+ }
+
+ current_dts += sc->stts_data[i].duration * sample_count;
+
+ if (current_dts > corrected_dts) {
+ int64_t drift = (current_dts - corrected_dts)/sample_count;
division by 0
A sample count of 0 is nonsensical. Sent a separate patch for 0 values
in stts. Will rebase this one on top.
Regards,
Gyan
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