dv: Mark internal frame reference as const

Silence a warning due to frame assignment in dvenc. All uses of the
reference in dvdec are read only, except the ones in the main decoding
function, so use the frame pointer directly there.

libavcodec/dv.h

@@ -39,7 +39,7 @@ typedef struct DVwork_chunk {
 
 typedef struct DVVideoContext {
     const AVDVProfile *sys;
-    AVFrame         *frame;
+    const AVFrame   *frame;
     AVCodecContext  *avctx;
     uint8_t         *buf;
 

libavcodec/dvdec.c

@@ -350,6 +350,7 @@ static int dvvideo_decode_frame(AVCodecContext *avctx, void *data,
     uint8_t *buf = avpkt->data;
     int buf_size = avpkt->size;
     DVVideoContext *s = avctx->priv_data;
+    AVFrame *frame = data;
     const uint8_t *vsc_pack;
     int apt, is16_9, ret;
     const AVDVProfile *sys;
@@ -369,9 +370,9 @@ static int dvvideo_decode_frame(AVCodecContext *avctx, void *data,
         s->sys = sys;
     }
 
-    s->frame            = data;
-    s->frame->key_frame = 1;
-    s->frame->pict_type = AV_PICTURE_TYPE_I;
+    s->frame            = frame;
+    frame->key_frame    = 1;
+    frame->pict_type    = AV_PICTURE_TYPE_I;
     avctx->pix_fmt      = s->sys->pix_fmt;
     avctx->framerate    = av_inv_q(s->sys->time_base);
 
@@ -388,12 +389,12 @@ static int dvvideo_decode_frame(AVCodecContext *avctx, void *data,
         ff_set_sar(avctx, s->sys->sar[is16_9]);
     }
 
-    if (ff_get_buffer(avctx, s->frame, 0) < 0) {
+    if (ff_get_buffer(avctx, frame, 0) < 0) {
         av_log(avctx, AV_LOG_ERROR, "get_buffer() failed\n");
         return -1;
     }
-    s->frame->interlaced_frame = 1;
-    s->frame->top_field_first  = 0;
+    frame->interlaced_frame = 1;
+    frame->top_field_first  = 0;
 
     s->buf = buf;
     avctx->execute(avctx, dv_decode_video_segment, s->work_chunks, NULL,