avcodec/mpegvideo_enc: Don't allocate buffers unnecessarily

ff_alloc_picture() performs two tasks: a) In most instances,
it allocates frame buffers and b) it allocates certain
auxiliary buffers.

The exception to a) is the case when the encoder can reuse
user-supplied frames. And for these frames the auxiliary buffers
are unused, because this frame will never be used as current_picture
(and therefore also not as next_picture or last_picture);
see select_input_picture().

This means that we can simply avoid calling ff_alloc_picture()
with user-supplied frames at all.

Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@outlook.com>

libavcodec/mpegpicture.c

@@ -246,7 +246,7 @@ static int alloc_picture_tables(AVCodecContext *avctx, Picture *pic, int encodin
  * The pixels are allocated/set by calling get_buffer() if shared = 0
  */
 int ff_alloc_picture(AVCodecContext *avctx, Picture *pic, MotionEstContext *me,
-                     ScratchpadContext *sc, int shared, int encoding,
+                     ScratchpadContext *sc, int encoding,
                      int chroma_x_shift, int chroma_y_shift, int out_format,
                      int mb_stride, int mb_width, int mb_height, int b8_stride,
                      ptrdiff_t *linesize, ptrdiff_t *uvlinesize)
@@ -258,10 +258,6 @@ int ff_alloc_picture(AVCodecContext *avctx, Picture *pic, MotionEstContext *me,
             || pic->alloc_mb_height != mb_height)
             free_picture_tables(pic);
 
-    if (shared) {
-        av_assert0(pic->f->data[0]);
-        pic->shared = 1;
-    } else {
         av_assert0(!pic->f->buf[0]);
         if (alloc_frame_buffer(avctx, pic, me, sc,
                                chroma_x_shift, chroma_y_shift,
@@ -270,7 +266,6 @@ int ff_alloc_picture(AVCodecContext *avctx, Picture *pic, MotionEstContext *me,
 
         *linesize   = pic->f->linesize[0];
         *uvlinesize = pic->f->linesize[1];
-    }
 
     if (!pic->qscale_table_buf)
         ret = alloc_picture_tables(avctx, pic, encoding, out_format,

libavcodec/mpegpicture.h

@@ -86,7 +86,7 @@ typedef struct Picture {
  * The pixels are allocated/set by calling get_buffer() if shared = 0.
  */
 int ff_alloc_picture(AVCodecContext *avctx, Picture *pic, MotionEstContext *me,
-                     ScratchpadContext *sc, int shared, int encoding,
+                     ScratchpadContext *sc, int encoding,
                      int chroma_x_shift, int chroma_y_shift, int out_format,
                      int mb_stride, int mb_width, int mb_height, int b8_stride,
                      ptrdiff_t *linesize, ptrdiff_t *uvlinesize);

libavcodec/mpegvideo_dec.c

@@ -236,7 +236,7 @@ int ff_mpv_common_frame_size_change(MpegEncContext *s)
 
 static int alloc_picture(MpegEncContext *s, Picture *pic)
 {
-    return ff_alloc_picture(s->avctx, pic, &s->me, &s->sc, 0, 0,
+    return ff_alloc_picture(s->avctx, pic, &s->me, &s->sc, 0,
                             s->chroma_x_shift, s->chroma_y_shift, s->out_format,
                             s->mb_stride, s->mb_width, s->mb_height, s->b8_stride,
                             &s->linesize, &s->uvlinesize);

libavcodec/mpegvideo_enc.c

@@ -1091,9 +1091,9 @@ static int get_intra_count(MpegEncContext *s, const uint8_t *src,
     return acc;
 }
 
-static int alloc_picture(MpegEncContext *s, Picture *pic, int shared)
+static int alloc_picture(MpegEncContext *s, Picture *pic)
 {
-    return ff_alloc_picture(s->avctx, pic, &s->me, &s->sc, shared, 1,
+    return ff_alloc_picture(s->avctx, pic, &s->me, &s->sc, 1,
                             s->chroma_x_shift, s->chroma_y_shift, s->out_format,
                             s->mb_stride, s->mb_width, s->mb_height, s->b8_stride,
                             &s->linesize, &s->uvlinesize);
@@ -1164,12 +1164,12 @@ static int load_input_picture(MpegEncContext *s, const AVFrame *pic_arg)
         if (direct) {
             if ((ret = av_frame_ref(pic->f, pic_arg)) < 0)
                 return ret;
-        }
-        ret = alloc_picture(s, pic, direct);
+            pic->shared = 1;
+        } else {
+            ret = alloc_picture(s, pic);
             if (ret < 0)
                 return ret;
 
-        if (!direct) {
             for (int i = 0; i < 3; i++) {
                 int src_stride = pic_arg->linesize[i];
                 int dst_stride = i ? s->uvlinesize : s->linesize;
@@ -1596,7 +1596,7 @@ no_output_pic:
             pic = &s->picture[i];
 
             pic->reference = s->reordered_input_picture[0]->reference;
-            ret = alloc_picture(s, pic, 0);
+            ret = alloc_picture(s, pic);
             if (ret < 0)
                 goto fail;