avfilter: take_samples: do not directly return frame when samples are skipped

Modifying data pointer when skipping samples may make it unaligned.
Workaround for Ticket6349.

This should fix the crash of ticket's testcase and a crash/regression
with avxsynth (reported by Michael Niedermayer).

Also change frame->nb_samples < max to frame->nb_samples <= max.
This improves performance. Benchmark:
./ffmpeg -filter_complex "aevalsrc=0:n=1166,firequalizer=fixed=on" -f null null
old:
  25767 decicycles in take_samples,    1023 runs,      1 skips
  25422 decicycles in take_samples,    2047 runs,      1 skips
  25181 decicycles in take_samples,    4095 runs,      1 skips
  24904 decicycles in take_samples,    8191 runs,      1 skips

new:
    550 decicycles in take_samples,    1024 runs,      0 skips
    548 decicycles in take_samples,    2048 runs,      0 skips
    545 decicycles in take_samples,    4096 runs,      0 skips
    544 decicycles in take_samples,    8192 runs,      0 skips

Reviewed-by: Nicolas George <george@nsup.org>
Reviewed-by: Michael Niedermayer <michael@niedermayer.cc>
Reviewed-by: Paul B Mahol <onemda@gmail.com>
Signed-off-by: Muhammad Faiz <mfcc64@gmail.com>

1 files changed, 7 insertions, 1 deletions

diff --git a/libavfilter/avfilter.c b/libavfilter/avfilter.c
index 08b86b010d..e60b0247bc 100644
--- a/libavfilter/avfilter.c
+++ b/libavfilter/avfilter.c
@@ -1191,7 +1191,7 @@ static int take_samples(AVFilterLink *link, unsigned min, unsigned max,
        called with enough samples. */
     av_assert1(samples_ready(link, link->min_samples));
     frame0 = frame = ff_framequeue_peek(&link->fifo, 0);
-    if (frame->nb_samples >= min && frame->nb_samples < max) {
+    if (!link->fifo.samples_skipped && frame->nb_samples >= min && frame->nb_samples <= max) {
         *rframe = ff_framequeue_take(&link->fifo);
         return 0;
     }
@@ -1522,6 +1522,12 @@ int ff_inlink_consume_frame(AVFilterLink *link, AVFrame **rframe)
     *rframe = NULL;
     if (!ff_inlink_check_available_frame(link))
         return 0;
+
+    if (link->fifo.samples_skipped) {
+        frame = ff_framequeue_peek(&link->fifo, 0);
+        return ff_inlink_consume_samples(link, frame->nb_samples, frame->nb_samples, rframe);
+    }
+
     frame = ff_framequeue_take(&link->fifo);
     consume_update(link, frame);
     *rframe = frame;