Build with newer FFmpeg

Index: Core/HLE/sceMpeg.cpp
--- Core/HLE/sceMpeg.cpp.orig
+++ Core/HLE/sceMpeg.cpp
@@ -719,7 +719,7 @@ static bool InitPmp(MpegContext * ctx){
 	pmp_want_pix_fmt = AV_PIX_FMT_RGBA;
 
 	// Create H264 video codec
-	AVCodec * pmp_Codec = avcodec_find_decoder(AV_CODEC_ID_H264);
+	const AVCodec * pmp_Codec = avcodec_find_decoder(AV_CODEC_ID_H264);
 	if (pmp_Codec == NULL){
 		ERROR_LOG(Log::Mpeg, "Can not find H264 codec, please update ffmpeg");
 		return false;
@@ -928,7 +928,7 @@ static bool decodePmpVideo(PSPPointer<SceMpegRingBuffe
 			avcodec_send_packet(pCodecCtx, &packet);
 		int len = avcodec_receive_frame(pCodecCtx, pFrame);
 		if (len == 0) {
-			len = pFrame->pkt_size;
+			len = packet.size;
 			got_picture = 1;
 		} else if (len == AVERROR(EAGAIN)) {
 			len = 0;
