From 3443330b172af9b45e11ecc3af4351a023f83d9c Mon Sep 17 00:00:00 2001
From: Andreas Rheinhardt <andreas.rheinhardt@outlook.com>
Date: Mon, 8 Aug 2022 13:06:54 +0200
Subject: [PATCH] avcodec/mpegvideo: Move setting mb_height to
 ff_mpv_init_context_frame

It is the proper place to set it, directly besides mb_width and
mb_stride. The reason for doing it the way it is done now seems
to be that the code does not create more slice contexts than necessary
(i.e. not more than one per row), so that this number needs to be
known before setting the number of slices. But this can always be
arranged by just moving the code that sets the number of slices.

Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@outlook.com>
---
 libavcodec/mpegvideo.c     | 32 ++++++++++++++++----------------
 libavcodec/mpegvideo_dec.c |  6 ------
 2 files changed, 16 insertions(+), 22 deletions(-)

diff --git a/libavcodec/mpegvideo.c b/libavcodec/mpegvideo.c
index 1405176c06..ff08168362 100644
--- a/libavcodec/mpegvideo.c
+++ b/libavcodec/mpegvideo.c
@@ -526,6 +526,11 @@ int ff_mpv_init_context_frame(MpegEncContext *s)
 {
     int y_size, c_size, yc_size, i, mb_array_size, mv_table_size, x, y;
 
+    if (s->codec_id == AV_CODEC_ID_MPEG2VIDEO && !s->progressive_sequence)
+        s->mb_height = (s->height + 31) / 32 * 2;
+    else
+        s->mb_height = (s->height + 15) / 16;
+
     s->mb_width   = (s->width + 15) / 16;
     s->mb_stride  = s->mb_width + 1;
     s->b8_stride  = s->mb_width * 2 + 1;
@@ -747,28 +752,12 @@ av_cold int ff_mpv_common_init(MpegEncContext *s)
     if (s->encoding && s->avctx->slices)
         nb_slices = s->avctx->slices;
 
-    if (s->codec_id == AV_CODEC_ID_MPEG2VIDEO && !s->progressive_sequence)
-        s->mb_height = (s->height + 31) / 32 * 2;
-    else
-        s->mb_height = (s->height + 15) / 16;
-
     if (s->avctx->pix_fmt == AV_PIX_FMT_NONE) {
         av_log(s->avctx, AV_LOG_ERROR,
                "decoding to AV_PIX_FMT_NONE is not supported.\n");
         return AVERROR(EINVAL);
     }
 
-    if (nb_slices > MAX_THREADS || (nb_slices > s->mb_height && s->mb_height)) {
-        int max_slices;
-        if (s->mb_height)
-            max_slices = FFMIN(MAX_THREADS, s->mb_height);
-        else
-            max_slices = MAX_THREADS;
-        av_log(s->avctx, AV_LOG_WARNING, "too many threads/slices (%d),"
-               " reducing to %d\n", nb_slices, max_slices);
-        nb_slices = max_slices;
-    }
-
     if ((s->width || s->height) &&
         av_image_check_size(s->width, s->height, 0, s->avctx))
         return AVERROR(EINVAL);
@@ -799,6 +788,17 @@ av_cold int ff_mpv_common_init(MpegEncContext *s)
     if ((ret = ff_mpv_init_context_frame(s)))
         goto fail;
 
+    if (nb_slices > MAX_THREADS || (nb_slices > s->mb_height && s->mb_height)) {
+        int max_slices;
+        if (s->mb_height)
+            max_slices = FFMIN(MAX_THREADS, s->mb_height);
+        else
+            max_slices = MAX_THREADS;
+        av_log(s->avctx, AV_LOG_WARNING, "too many threads/slices (%d),"
+               " reducing to %d\n", nb_slices, max_slices);
+        nb_slices = max_slices;
+    }
+
 #if FF_API_FLAG_TRUNCATED
     s->parse_context.state = -1;
 #endif
diff --git a/libavcodec/mpegvideo_dec.c b/libavcodec/mpegvideo_dec.c
index 7caaf0596d..93ba4e31b3 100644
--- a/libavcodec/mpegvideo_dec.c
+++ b/libavcodec/mpegvideo_dec.c
@@ -208,12 +208,6 @@ int ff_mpv_common_frame_size_change(MpegEncContext *s)
     s->next_picture_ptr         =
     s->current_picture_ptr      = NULL;
 
-    // init
-    if (s->codec_id == AV_CODEC_ID_MPEG2VIDEO && !s->progressive_sequence)
-        s->mb_height = (s->height + 31) / 32 * 2;
-    else
-        s->mb_height = (s->height + 15) / 16;
-
     if ((s->width || s->height) &&
         (err = av_image_check_size(s->width, s->height, 0, s->avctx)) < 0)
         goto fail;