[Spice-devel] [PATCH] spice.h: Don't use 48kHz for playback/recording rates

[Christophe Fergeau]

When adding Opus support, SPICE_INTERFACE_PLAYBACK_FREQ and
SPICE_INTERFACE_RECORD_FREQ in the public header 'spice.h' were changed
from 44100 to 48000.
However, this was not really useful as these constants are not used in
spice-server, but only by users of spice-server (ie QEMU).
It turns out changing these values is actually harmful. QEMU uses these
constants in 2 situations:
1. when it's a version of QEMU with this commit, but we are compiling
   against older spice-server headers (before Opus support was added)
2. when it's a version of QEMU without commit 795ca114d35 which added
   what is needed for Opus support

When we are in the second situation, having 48000 in the public header
will actually cause issues as spice-server will know QEMU does not
support Opus, so internally spice-server will be using a 44100 rate for
audio. However, QEMU will be using SPICE_INTERFACE_.*_FREQ and think it
should use a 48000 rate, which will cause distorsions as experienced in
bug https://bugzilla.redhat.com/show_bug.cgi?id=1129961

Reverting these constants back to 44100 will fix audio in the 'new
spice-server/old QEMU' scenario, and won't cause issues either when both
support Opus as in this case these constants are not used.
---
 server/spice.h | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/server/spice.h b/server/spice.h
index c648a1d..58700d1 100644
--- a/server/spice.h
+++ b/server/spice.h
@@ -342,7 +342,7 @@ enum {
     SPICE_INTERFACE_AUDIO_FMT_S16 = 1,
 };
 
-#define SPICE_INTERFACE_PLAYBACK_FREQ  48000
+#define SPICE_INTERFACE_PLAYBACK_FREQ  44100
 #define SPICE_INTERFACE_PLAYBACK_CHAN  2
 #define SPICE_INTERFACE_PLAYBACK_FMT   SPICE_INTERFACE_AUDIO_FMT_S16
 
@@ -372,7 +372,7 @@ typedef struct SpiceRecordInterface SpiceRecordInterface;
 typedef struct SpiceRecordInstance SpiceRecordInstance;
 typedef struct SpiceRecordState SpiceRecordState;
 
-#define SPICE_INTERFACE_RECORD_FREQ  48000
+#define SPICE_INTERFACE_RECORD_FREQ  44100
 #define SPICE_INTERFACE_RECORD_CHAN  2
 #define SPICE_INTERFACE_RECORD_FMT   SPICE_INTERFACE_AUDIO_FMT_S16
 
-- 
1.9.3