audio: fix bug 1858488

The combined generic buffer management code and buffer run out
code in function audio_generic_put_buffer_out has a problematic
behaviour. A few hundred milliseconds after playback starts the
mixing buffer and the generic buffer are nearly full and the
following pattern can be seen.

On first call of audio_pcm_hw_run_out the buffer run code in
audio_generic_put_buffer_out writes some data to the audio
hardware but the generic buffer will fill faster and is full
when audio_pcm_hw_run_out returns. This is because emulated
audio devices can produce playback data at a higher rate than
the audio backend hardware consumes this data.

On next call of audio_pcm_hw_run_out the buffer run code in
audio_generic_put_buffer_out writes some data to the audio
hardware but no audio data is transferred to the generic buffer
because the buffer is already full.

Then the pattern repeats. For the emulated audio device this
looks like the audio timer period has doubled.

This patch splits the combined generic buffer management code
and buffer run out code and calls the buffer run out code after
buffer management code to break this pattern.

The bug report is for the wav audio backend. But the problem is
not limited to this backend. All audio backends which use the
audio_generic_put_buffer_out function show this problem.

Buglink: https://bugs.launchpad.net/qemu/+bug/1858488
Signed-off-by: Volker Rümelin <vr_qemu@t-online.de>
Message-Id: <20200123074943.6699-5-vr_qemu@t-online.de>
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>

diff --git a/audio/alsaaudio.c b/audio/alsaaudio.c
index f37ce1ce85705388c5fd88d760cc0de4f5e98181..4ef26818be57c0e47385a27336b38d1c74bf6f02 100644 (file)
--- a/audio/alsaaudio.c
+++ b/audio/alsaaudio.c
@@ -906,6 +906,7 @@ static struct audio_pcm_ops alsa_pcm_ops = {
     .init_out = alsa_init_out,
     .fini_out = alsa_fini_out,
     .write    = alsa_write,
+    .run_buffer_out = audio_generic_run_buffer_out,
     .enable_out = alsa_enable_out,
 
     .init_in  = alsa_init_in,

diff --git a/audio/audio.c b/audio/audio.c
index 12ed318813f4c6ffd4447f571b04cf0b6b84f82d..b686429203d65b19e497b1351499c3a78a71f56e 100644 (file)
--- a/audio/audio.c
+++ b/audio/audio.c
@@ -1097,6 +1097,10 @@ static size_t audio_pcm_hw_run_out(HWVoiceOut *hw, size_t live)
         }
     }
 
+    if (hw->pcm_ops->run_buffer_out) {
+        hw->pcm_ops->run_buffer_out(hw);
+    }
+
     return clipped;
 }
 
@@ -1413,6 +1417,28 @@ void audio_generic_put_buffer_in(HWVoiceIn *hw, void *buf, size_t size)
     hw->pending_emul -= size;
 }
 
+void audio_generic_run_buffer_out(HWVoiceOut *hw)
+{
+    while (hw->pending_emul) {
+        size_t write_len, written;
+        ssize_t start = ((ssize_t) hw->pos_emul) - hw->pending_emul;
+
+        if (start < 0) {
+            start += hw->size_emul;
+        }
+        assert(start >= 0 && start < hw->size_emul);
+
+        write_len = MIN(hw->pending_emul, hw->size_emul - start);
+
+        written = hw->pcm_ops->write(hw, hw->buf_emul + start, write_len);
+        hw->pending_emul -= written;
+
+        if (written < write_len) {
+            break;
+        }
+    }
+}
+
 void *audio_generic_get_buffer_out(HWVoiceOut *hw, size_t *size)
 {
     if (unlikely(!hw->buf_emul)) {
@@ -1428,8 +1454,7 @@ void *audio_generic_get_buffer_out(HWVoiceOut *hw, size_t *size)
     return hw->buf_emul + hw->pos_emul;
 }
 
-size_t audio_generic_put_buffer_out_nowrite(HWVoiceOut *hw, void *buf,
-                                            size_t size)
+size_t audio_generic_put_buffer_out(HWVoiceOut *hw, void *buf, size_t size)
 {
     assert(buf == hw->buf_emul + hw->pos_emul &&
            size + hw->pending_emul <= hw->size_emul);
@@ -1440,35 +1465,6 @@ size_t audio_generic_put_buffer_out_nowrite(HWVoiceOut *hw, void *buf,
     return size;
 }
 
-size_t audio_generic_put_buffer_out(HWVoiceOut *hw, void *buf, size_t size)
-{
-    audio_generic_put_buffer_out_nowrite(hw, buf, size);
-
-    while (hw->pending_emul) {
-        size_t write_len, written;
-        ssize_t start = ((ssize_t) hw->pos_emul) - hw->pending_emul;
-        if (start < 0) {
-            start += hw->size_emul;
-        }
-        assert(start >= 0 && start < hw->size_emul);
-
-        write_len = MIN(hw->pending_emul, hw->size_emul - start);
-
-        written = hw->pcm_ops->write(hw, hw->buf_emul + start, write_len);
-        hw->pending_emul -= written;
-
-        if (written < write_len) {
-            break;
-        }
-    }
-
-    /*
-     * fake we have written everything. non-written data remain in pending_emul,
-     * so we do not have to clip them multiple times
-     */
-    return size;
-}
-
 size_t audio_generic_write(HWVoiceOut *hw, void *buf, size_t size)
 {
     size_t dst_size, copy_size;

diff --git a/audio/audio_int.h b/audio/audio_int.h
index 5ba20783463a7badc6c184409112ab0d7a20aea1..3c8e48b55b1c062b3845ba98a6646c5457f04af4 100644 (file)
--- a/audio/audio_int.h
+++ b/audio/audio_int.h
@@ -152,6 +152,7 @@ struct audio_pcm_ops {
     int    (*init_out)(HWVoiceOut *hw, audsettings *as, void *drv_opaque);
     void   (*fini_out)(HWVoiceOut *hw);
     size_t (*write)   (HWVoiceOut *hw, void *buf, size_t size);
+    void   (*run_buffer_out)(HWVoiceOut *hw);
     /*
      * get a buffer that after later can be passed to put_buffer_out; optional
      * returns the buffer, and writes it's size to size (in bytes)
@@ -178,10 +179,9 @@ struct audio_pcm_ops {
 
 void *audio_generic_get_buffer_in(HWVoiceIn *hw, size_t *size);
 void audio_generic_put_buffer_in(HWVoiceIn *hw, void *buf, size_t size);
+void audio_generic_run_buffer_out(HWVoiceOut *hw);
 void *audio_generic_get_buffer_out(HWVoiceOut *hw, size_t *size);
 size_t audio_generic_put_buffer_out(HWVoiceOut *hw, void *buf, size_t size);
-size_t audio_generic_put_buffer_out_nowrite(HWVoiceOut *hw, void *buf,
-                                            size_t size);
 size_t audio_generic_write(HWVoiceOut *hw, void *buf, size_t size);
 size_t audio_generic_read(HWVoiceIn *hw, void *buf, size_t size);
 

diff --git a/audio/coreaudio.c b/audio/coreaudio.c
index 66f0f459cf09f9f796342eb89e6df929bddc3a70..c7a7196c2d5358b79401449280440d416bd991c3 100644 (file)
--- a/audio/coreaudio.c
+++ b/audio/coreaudio.c
@@ -411,7 +411,7 @@ static int coreaudio_unlock (coreaudioVoiceOut *core, const char *fn_name)
     }
 COREAUDIO_WRAPPER_FUNC(get_buffer_out, void *, (HWVoiceOut *hw, size_t *size),
                        (hw, size))
-COREAUDIO_WRAPPER_FUNC(put_buffer_out_nowrite, size_t,
+COREAUDIO_WRAPPER_FUNC(put_buffer_out, size_t,
                        (HWVoiceOut *hw, void *buf, size_t size),
                        (hw, buf, size))
 COREAUDIO_WRAPPER_FUNC(write, size_t, (HWVoiceOut *hw, void *buf, size_t size),
@@ -687,9 +687,12 @@ static void coreaudio_audio_fini (void *opaque)
 static struct audio_pcm_ops coreaudio_pcm_ops = {
     .init_out = coreaudio_init_out,
     .fini_out = coreaudio_fini_out,
+  /* wrapper for audio_generic_write */
     .write    = coreaudio_write,
+  /* wrapper for audio_generic_get_buffer_out */
     .get_buffer_out = coreaudio_get_buffer_out,
-    .put_buffer_out = coreaudio_put_buffer_out_nowrite,
+  /* wrapper for audio_generic_put_buffer_out */
+    .put_buffer_out = coreaudio_put_buffer_out,
     .enable_out = coreaudio_enable_out
 };
 

diff --git a/audio/noaudio.c b/audio/noaudio.c
index ff99b253ff0b86e940cff37fc6bc5a6c130cb819..05798ea210325cceab6e74184ec67dc38a4db5c7 100644 (file)
--- a/audio/noaudio.c
+++ b/audio/noaudio.c
@@ -118,6 +118,7 @@ static struct audio_pcm_ops no_pcm_ops = {
     .init_out = no_init_out,
     .fini_out = no_fini_out,
     .write    = no_write,
+    .run_buffer_out = audio_generic_run_buffer_out,
     .enable_out = no_enable_out,
 
     .init_in  = no_init_in,

diff --git a/audio/ossaudio.c b/audio/ossaudio.c
index 94564916fbf03c4783a5fdf5c4031336757f16c8..576b5b5b20210c3c0bd7eaebabbb815d801f5aa2 100644 (file)
--- a/audio/ossaudio.c
+++ b/audio/ossaudio.c
@@ -382,6 +382,15 @@ static size_t oss_get_available_bytes(OSSVoiceOut *oss)
     return audio_ring_dist(cntinfo.ptr, oss->hw.pos_emul, oss->hw.size_emul);
 }
 
+static void oss_run_buffer_out(HWVoiceOut *hw)
+{
+    OSSVoiceOut *oss = (OSSVoiceOut *)hw;
+
+    if (!oss->mmapped) {
+        audio_generic_run_buffer_out(hw);
+    }
+}
+
 static void *oss_get_buffer_out(HWVoiceOut *hw, size_t *size)
 {
     OSSVoiceOut *oss = (OSSVoiceOut *) hw;
@@ -748,6 +757,7 @@ static struct audio_pcm_ops oss_pcm_ops = {
     .init_out = oss_init_out,
     .fini_out = oss_fini_out,
     .write    = oss_write,
+    .run_buffer_out = oss_run_buffer_out,
     .get_buffer_out = oss_get_buffer_out,
     .put_buffer_out = oss_put_buffer_out,
     .enable_out = oss_enable_out,

diff --git a/audio/sdlaudio.c b/audio/sdlaudio.c
index 5c6bcfcb3e9d9b86277128b832f6b3178e4b1050..c00e7d7845234823e8a06d77c4e06c1983baa18f 100644 (file)
--- a/audio/sdlaudio.c
+++ b/audio/sdlaudio.c
@@ -227,7 +227,7 @@ static void sdl_callback (void *opaque, Uint8 *buf, int len)
 
 SDL_WRAPPER_FUNC(get_buffer_out, void *, (HWVoiceOut *hw, size_t *size),
                  (hw, size), *size = 0, sdl_unlock)
-SDL_WRAPPER_FUNC(put_buffer_out_nowrite, size_t,
+SDL_WRAPPER_FUNC(put_buffer_out, size_t,
                  (HWVoiceOut *hw, void *buf, size_t size), (hw, buf, size),
                  /*nothing*/, sdl_unlock_and_post)
 SDL_WRAPPER_FUNC(write, size_t,
@@ -320,9 +320,12 @@ static void sdl_audio_fini (void *opaque)
 static struct audio_pcm_ops sdl_pcm_ops = {
     .init_out = sdl_init_out,
     .fini_out = sdl_fini_out,
+  /* wrapper for audio_generic_write */
     .write    = sdl_write,
+  /* wrapper for audio_generic_get_buffer_out */
     .get_buffer_out = sdl_get_buffer_out,
-    .put_buffer_out = sdl_put_buffer_out_nowrite,
+  /* wrapper for audio_generic_put_buffer_out */
+    .put_buffer_out = sdl_put_buffer_out,
     .enable_out = sdl_enable_out,
 };
 

diff --git a/audio/wavaudio.c b/audio/wavaudio.c
index e46d834bd3af26afe23563a7d2b959eae1ef9e46..20e6853f85861f7bfb5e5a610c43ec9da6f7e0ca 100644 (file)
--- a/audio/wavaudio.c
+++ b/audio/wavaudio.c
@@ -197,6 +197,7 @@ static struct audio_pcm_ops wav_pcm_ops = {
     .init_out = wav_init_out,
     .fini_out = wav_fini_out,
     .write    = wav_write_out,
+    .run_buffer_out = audio_generic_run_buffer_out,
     .enable_out = wav_enable_out,
 };