diff --git a/libao2/ao_pcm.c b/libao2/ao_pcm.c
index bfcd8eb79f..10ee82a0e2 100644
--- a/libao2/ao_pcm.c
+++ b/libao2/ao_pcm.c
@@ -61,30 +61,75 @@ static int fast = 0;
 #define WAV_ID_DATA 0x61746164 /* "data" */
 #define WAV_ID_PCM  0x0001
 #define WAV_ID_FLOAT_PCM  0x0003
-
-struct WaveHeader
-{
-    uint32_t riff;
-    uint32_t file_length;
-    uint32_t wave;
-    uint32_t fmt;
-    uint32_t fmt_length;
-    uint16_t fmt_tag;
-    uint16_t channels;
-    uint32_t sample_rate;
-    uint32_t bytes_per_second;
-    uint16_t block_align;
-    uint16_t bits;
-    uint32_t data;
-    uint32_t data_length;
-};
+#define WAV_ID_FORMAT_EXTENSIBLE 0xfffe
 
 /* init with default values */
-static struct WaveHeader wavhdr;
 static uint64_t data_length;
-
 static FILE *fp = NULL;
 
+
+static void fput16le(uint16_t val, FILE *fp) {
+    uint8_t bytes[2] = {val, val >> 8};
+    fwrite(bytes, 1, 2, fp);
+}
+
+static void fput32le(uint32_t val, FILE *fp) {
+    uint8_t bytes[4] = {val, val >> 8, val >> 16, val >> 24};
+    fwrite(bytes, 1, 4, fp);
+}
+
+static void write_wave_header(FILE *fp, uint64_t data_length) {
+    int use_waveex = (ao_data.channels >= 5 && ao_data.channels <= 8);
+    uint16_t fmt = (ao_data.format == AF_FORMAT_FLOAT_LE) ? WAV_ID_FLOAT_PCM : WAV_ID_PCM;
+    uint32_t fmt_chunk_size = use_waveex ? 40 : 16;
+    int bits = af_fmt2bits(ao_data.format);
+
+    // Master RIFF chunk
+    fput32le(WAV_ID_RIFF, fp);
+    // RIFF chunk size: 'WAVE' + 'fmt ' + 4 + fmt_chunk_size + data chunk hdr (8) + data length
+    fput32le(12 + fmt_chunk_size + 8 + data_length, fp);
+    fput32le(WAV_ID_WAVE, fp);
+
+    // Format chunk
+    fput32le(WAV_ID_FMT, fp);
+    fput32le(fmt_chunk_size, fp);
+    fput16le(use_waveex ? WAV_ID_FORMAT_EXTENSIBLE : fmt, fp);
+    fput16le(ao_data.channels, fp);
+    fput32le(ao_data.samplerate, fp);
+    fput32le(ao_data.bps, fp);
+    fput16le(ao_data.channels * (bits / 8), fp);
+    fput16le(bits, fp);
+
+    if (use_waveex) {
+        // Extension chunk
+        fput16le(22, fp);
+        fput16le(bits, fp);
+        switch (ao_data.channels) {
+            case 5:
+                fput32le(0x0607, fp); // L R C Lb Rb
+                break;
+            case 6:
+                fput32le(0x060f, fp); // L R C Lb Rb LFE
+                break;
+            case 7:
+                fput32le(0x0727, fp); // L R C Cb Ls Rs LFE
+                break;
+            case 8:
+                fput32le(0x063f, fp); // L R C Lb Rb Ls Rs LFE
+                break;
+        }
+        // 2 bytes format + 14 bytes guid
+        fput32le(fmt, fp);
+        fput32le(0x00100000, fp);
+        fput32le(0xAA000080, fp);
+        fput32le(0x719B3800, fp);
+    }
+
+    // Data chunk
+    fput32le(WAV_ID_DATA, fp);
+    fput32le(data_length, fp);
+}
+
 // to set/get/query special features/parameters
 static int control(int cmd,void *arg){
     return -1;
@@ -93,7 +138,6 @@ static int control(int cmd,void *arg){
 // open & setup audio device
 // return: 1=success 0=fail
 static int init(int rate,int channels,int format,int flags){
-    int bits;
     const opt_t subopts[] = {
         {"waveheader", OPT_ARG_BOOL, &ao_pcm_waveheader, NULL},
         {"file",       OPT_ARG_MSTRZ, &ao_outputfilename, NULL},
@@ -130,29 +174,12 @@ static int init(int rate,int channels,int format,int flags){
         }
     }
 
-    bits = af_fmt2bits(format);
-
     ao_data.outburst = 65536;
     ao_data.buffersize= 2*65536;
     ao_data.channels=channels;
     ao_data.samplerate=rate;
     ao_data.format=format;
-    ao_data.bps=channels*rate*(bits/8);
-
-    wavhdr.riff = le2me_32(WAV_ID_RIFF);
-    wavhdr.wave = le2me_32(WAV_ID_WAVE);
-    wavhdr.fmt = le2me_32(WAV_ID_FMT);
-    wavhdr.fmt_length = le2me_32(16);
-    wavhdr.fmt_tag = le2me_16(format == AF_FORMAT_FLOAT_LE ? WAV_ID_FLOAT_PCM : WAV_ID_PCM);
-    wavhdr.channels = le2me_16(ao_data.channels);
-    wavhdr.sample_rate = le2me_32(ao_data.samplerate);
-    wavhdr.bytes_per_second = le2me_32(ao_data.bps);
-    wavhdr.bits = le2me_16(bits);
-    wavhdr.block_align = le2me_16(ao_data.channels * (bits / 8));
-
-    wavhdr.data = le2me_32(WAV_ID_DATA);
-    wavhdr.data_length=le2me_32(0x7ffff000);
-    wavhdr.file_length = wavhdr.data_length + sizeof(wavhdr) - 8;
+    ao_data.bps=channels*rate*(af_fmt2bits(format)/8);
 
     mp_msg(MSGT_AO, MSGL_INFO, MSGTR_AO_PCM_FileInfo, ao_outputfilename,
            (ao_pcm_waveheader?"WAVE":"RAW PCM"), rate,
@@ -162,7 +189,7 @@ static int init(int rate,int channels,int format,int flags){
     fp = fopen(ao_outputfilename, "wb");
     if(fp) {
         if(ao_pcm_waveheader){ /* Reserve space for wave header */
-            fwrite(&wavhdr,sizeof(wavhdr),1,fp);
+            write_wave_header(fp, 0x7ffff000);
         }
         return 1;
     }
@@ -186,10 +213,7 @@ static void uninit(int immed){
         else if (data_length > 0x7ffff000)
             mp_msg(MSGT_AO, MSGL_ERR, "File larger than allowed for WAV files, may play truncated!\n");
         else {
-            wavhdr.file_length = data_length + sizeof(wavhdr) - 8;
-            wavhdr.file_length = le2me_32(wavhdr.file_length);
-            wavhdr.data_length = le2me_32(data_length);
-            fwrite(&wavhdr,sizeof(wavhdr),1,fp);
+            write_wave_header(fp, data_length);
         }
     }
     fclose(fp);
@@ -241,7 +265,7 @@ static int play(void* data,int len,int flags){
 #endif
 
     if (ao_data.channels == 5 || ao_data.channels == 6 || ao_data.channels == 8) {
-        int frame_size = le2me_16(wavhdr.bits) / 8;
+        int frame_size = af_fmt2bits(ao_data.format) / 8;
         len -= len % (frame_size * ao_data.channels);
         reorder_channel_nch(data, AF_CHANNEL_LAYOUT_MPLAYER_DEFAULT,
                             AF_CHANNEL_LAYOUT_WAVEEX_DEFAULT,