Initialize riff and wav size fields to -1 instead of 0.

WMP doess not play the output files if the fields are
set to 0 and not overwritten (using pipe output).

Fixes ticket #3346.

libavformat/riffenc.c

@@ -31,7 +31,7 @@
 int64_t ff_start_tag(AVIOContext *pb, const char *tag)
 {
     ffio_wfourcc(pb, tag);
-    avio_wl32(pb, 0);
+    avio_wl32(pb, -1);
     return avio_tell(pb);
 }
 

libavformat/wavenc.c

@@ -126,7 +126,7 @@ static int wav_write_header(AVFormatContext *s)
         avio_wl32(pb, -1); /* RF64 chunk size: use size in ds64 */
     } else {
         ffio_wfourcc(pb, "RIFF");
-        avio_wl32(pb, 0); /* file length */
+        avio_wl32(pb, -1); /* file length */
     }
 
     ffio_wfourcc(pb, "WAVE");

tests/fate/filter-audio.mak

@@ -58,7 +58,7 @@ fate-filter-channelmap-one-int: SRC = $(TARGET_PATH)/tests/data/asynth-44100-6.w
 fate-filter-channelmap-one-int: tests/data/asynth-44100-6.wav
 fate-filter-channelmap-one-int: CMD = md5 -i $(SRC) -filter_complex_script $(TARGET_PATH)/tests/data/filtergraphs/channelmap_one_int -f wav -flags +bitexact
 fate-filter-channelmap-one-int: CMP = oneline
-fate-filter-channelmap-one-int: REF = 06168d06085e2c0603e4e118ba4cade2
+fate-filter-channelmap-one-int: REF = 428b8f9fac6d57147069b97335019ef5
 
 FATE_FILTER_CHANNELMAP += fate-filter-channelmap-one-str
 fate-filter-channelmap-one-str: tests/data/filtergraphs/channelmap_one_str
@@ -66,7 +66,7 @@ fate-filter-channelmap-one-str: SRC = $(TARGET_PATH)/tests/data/asynth-44100-2.w
 fate-filter-channelmap-one-str: tests/data/asynth-44100-2.wav
 fate-filter-channelmap-one-str: CMD = md5 -i $(SRC) -filter_complex_script $(TARGET_PATH)/tests/data/filtergraphs/channelmap_one_str -f wav -flags +bitexact
 fate-filter-channelmap-one-str: CMP = oneline
-fate-filter-channelmap-one-str: REF = 49ed4aaec717f1b28137c9e1f01f343b
+fate-filter-channelmap-one-str: REF = e788890db6a11c2fb29d7c4229072d49
 
 FATE_AFILTER-$(call FILTERDEMDECENCMUX, CHANNELMAP, WAV, PCM_S16LE, PCM_S16LE, WAV) += $(FATE_FILTER_CHANNELMAP)
 

tests/ref/fate/mapchan-6ch-extract-2

-3be6f8cefbf3c2e6dce670ee190b4313
-b8791d1c07de59dd1badf2c7b5f62a74
+955514d4a026a4a48695866d2ec904d0
+498a49e692ee2e3c454863654275c4bb

tests/ref/fate/mapchan-6ch-extract-2-downmix-mono

-e02d9537df5f534d14937bf7ab9b9a40
+2727e5418eb5b8f89954f140d9f3a19a

tests/ref/fate/mapchan-silent-mono

-c37237a92bcf708bc0e20b713665a5a7
+16dc73c037897dff9b1d3e3d8561dc73

tests/ref/fate/v410enc

-e5c0b1f17d2a64a416dcf9bf7a38d9d9
+f7cf1b743c18f74d047ce8d6ea05d3d9