avcodec/yuv4enc: Avoid copying packet data, allow user-supplied buffers

When the packet size is known in advance like here, one can avoid
an intermediate buffer for the packet data by using
ff_get_encode_buffer() and also set AV_CODEC_CAP_DR1 at the same time.

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

libavcodec/yuv4enc.c

@@ -21,6 +21,7 @@
  */
 
 #include "avcodec.h"
+#include "encode.h"
 #include "internal.h"
 
 static int yuv4_encode_frame(AVCodecContext *avctx, AVPacket *pkt,
@@ -30,7 +31,9 @@ static int yuv4_encode_frame(AVCodecContext *avctx, AVPacket *pkt,
     uint8_t *y, *u, *v;
     int i, j, ret;
 
-    if ((ret = ff_alloc_packet2(avctx, pkt, 6 * (avctx->width + 1 >> 1) * (avctx->height + 1 >> 1), 0)) < 0)
+    ret = ff_get_encode_buffer(avctx, pkt, 6 * (avctx->width  + 1 >> 1)
+                                             * (avctx->height + 1 >> 1), 0);
+    if (ret < 0)
         return ret;
     dst = pkt->data;
 
@@ -62,6 +65,7 @@ const AVCodec ff_yuv4_encoder = {
     .long_name    = NULL_IF_CONFIG_SMALL("Uncompressed packed 4:2:0"),
     .type         = AVMEDIA_TYPE_VIDEO,
     .id           = AV_CODEC_ID_YUV4,
+    .capabilities = AV_CODEC_CAP_DR1,
     .encode2      = yuv4_encode_frame,
     .pix_fmts     = (const enum AVPixelFormat[]){ AV_PIX_FMT_YUV420P, AV_PIX_FMT_NONE },
 };