Revert commit 0bc39128

        ffmpeg: remove -psnr option.

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

ffmpeg.c

@@ -134,6 +134,7 @@ static int file_overwrite = 0;
 static int do_benchmark = 0;
 static int do_hex_dump = 0;
 static int do_pkt_dump = 0;
+static int do_psnr = 0;
 static int do_pass = 0;
 static const char *pass_logfilename_prefix;
 static int video_sync_method= -1;
@@ -3660,6 +3661,9 @@ static OutputStream *new_video_stream(OptionsContext *o, AVFormatContext *oc)
             video_enc->rc_initial_buffer_occupancy = video_enc->rc_buffer_size*3/4;
         video_enc->intra_dc_precision= intra_dc_precision - 8;
 
+        if (do_psnr)
+            video_enc->flags|= CODEC_FLAG_PSNR;
+
         /* two pass mode */
         if (do_pass) {
             if (do_pass & 1) {
@@ -4624,6 +4628,7 @@ static const OptionDef options[] = {
     { "passlogfile", HAS_ARG | OPT_VIDEO, {(void*)&opt_passlogfile}, "select two pass log file name prefix", "prefix" },
     { "deinterlace", OPT_BOOL | OPT_EXPERT | OPT_VIDEO, {(void*)&do_deinterlace},
       "deinterlace pictures" },
+    { "psnr", OPT_BOOL | OPT_EXPERT | OPT_VIDEO, {(void*)&do_psnr}, "calculate PSNR of compressed frames" },
     { "vstats", OPT_EXPERT | OPT_VIDEO, {(void*)&opt_vstats}, "dump video coding statistics to file" },
     { "vstats_file", HAS_ARG | OPT_EXPERT | OPT_VIDEO, {(void*)opt_vstats_file}, "dump video coding statistics to file", "file" },
 #if CONFIG_AVFILTER