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avcodec/mpeg12dec: Don't reinit upon aspect ratio change

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The spec indeed does not allow the aspect ratio to change
within a video sequence, but this does not imply that we
must reinitialize the decoder if only the aspect ratio changes,
as this value does not affect the decoding process at all.
Moreover, our reinitialization is a bit buggy: If there is
frame reordering, then the not yet output next P-frame is
simply discarded upon reinit. With this patch this no longer
happens when only the aspect ratio changes.

Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@outlook.com>
This commit is contained in:
Andreas Rheinhardt
2025-04-30 18:20:51 +02:00
parent 554b52b1b3
commit 1f0af6b592
1 changed files with 0 additions and 3 deletions
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3
libavcodec/mpeg12dec.c
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@ -80,7 +80,6 @@ typedef struct Mpeg1Context {
int has_afd;
int slice_count;
unsigned aspect_ratio_info;
AVRational save_aspect;
int save_width, save_height, save_progressive_seq;
AVRational frame_rate_ext; /* MPEG-2 specific framerate modificator */
unsigned frame_rate_index;
@ -918,7 +917,6 @@ static int mpeg_decode_postinit(AVCodecContext *avctx)
avctx->coded_height != s->height ||
s1->save_width != s->width ||
s1->save_height != s->height ||
av_cmp_q(s1->save_aspect, s->avctx->sample_aspect_ratio) ||
(s1->save_progressive_seq != s->progressive_sequence && FFALIGN(s->height, 16) != FFALIGN(s->height, 32)) ||
0) {
if (s->context_initialized)
@ -935,7 +933,6 @@ static int mpeg_decode_postinit(AVCodecContext *avctx)
(s1->bit_rate != 0x3FFFF*400 || s1->vbv_delay != 0xFFFF)) {
avctx->bit_rate = s1->bit_rate;
}
s1->save_aspect = s->avctx->sample_aspect_ratio;
s1->save_width = s->width;
s1->save_height = s->height;
s1->save_progressive_seq = s->progressive_sequence;