Do not memcpy raw video frames when using null muxer

Commit 035af998 made avconv always call an encoder when using the
null muxer.  While useful for 2-pass encodes, it inadvertently
caused an extra memcpy of raw frames when decoding only.

This hack restores the old behaviour when only decoding while
allowing use of the null muxer with encoded streams as well.
Signed-off-by: Mans Rullgard <mans@mansr.com>

avconv.c

@@ -1207,7 +1207,8 @@ static void do_video_out(AVFormatContext *s,
         av_init_packet(&pkt);
         pkt.stream_index= ost->index;
 
-        if (s->oformat->flags & AVFMT_RAWPICTURE) {
+        if (s->oformat->flags & AVFMT_RAWPICTURE &&
+            enc->codec->id == CODEC_ID_RAWVIDEO) {
             /* raw pictures are written as AVPicture structure to
                avoid any copies. We support temporarily the older
                method. */
@@ -1459,7 +1460,7 @@ static void flush_encoders(OutputStream *ost_table, int nb_ostreams)
 
         if (ost->st->codec->codec_type == AVMEDIA_TYPE_AUDIO && enc->frame_size <=1)
             continue;
-        if (ost->st->codec->codec_type == AVMEDIA_TYPE_VIDEO && (os->oformat->flags & AVFMT_RAWPICTURE))
+        if (ost->st->codec->codec_type == AVMEDIA_TYPE_VIDEO && (os->oformat->flags & AVFMT_RAWPICTURE) && enc->codec->id == CODEC_ID_RAWVIDEO)
             continue;
 
         for(;;) {

libavformat/nullenc.c

@@ -32,5 +32,5 @@ AVOutputFormat ff_null_muxer = {
     .audio_codec       = AV_NE(CODEC_ID_PCM_S16BE, CODEC_ID_PCM_S16LE),
     .video_codec       = CODEC_ID_RAWVIDEO,
     .write_packet      = null_write_packet,
-    .flags = AVFMT_NOFILE | AVFMT_NOTIMESTAMPS,
+    .flags = AVFMT_NOFILE | AVFMT_NOTIMESTAMPS | AVFMT_RAWPICTURE,
 };