/* handle p-frames only if a predecessor frame is available */
if (s->prev->data[0]) {
- if ( !(avpkt->flags & AV_PKT_FLAG_KEY)
+ if ( !(avpkt->flags & AV_PKT_FLAG_KEY) && avctx->codec_tag != AV_RL32("MPNG")
&& s->prev->width == p->width
&& s->prev->height== p->height
&& s->prev->format== p->format