Re: [Qemu-devel] [PATCH v2 03/14] audio: add audiodev property to vnc and wav_capture

[Markus Armbruster]

"Kővágó, Zoltán" <address@hidden> writes:

> Signed-off-by: Kővágó, Zoltán <address@hidden>
> ---
>  ui/vnc.h        |  2 ++
>  monitor/misc.c  | 12 +++++++++++-
>  ui/vnc.c        | 15 ++++++++++++++-
>  hmp-commands.hx | 13 ++++++++-----
>  qemu-options.hx |  6 ++++++
>  5 files changed, 41 insertions(+), 7 deletions(-)
>
> diff --git a/ui/vnc.h b/ui/vnc.h
> index 2f84db3142..6f54653455 100644
> --- a/ui/vnc.h
> +++ b/ui/vnc.h
> @@ -183,6 +183,8 @@ struct VncDisplay
>  #ifdef CONFIG_VNC_SASL
>      VncDisplaySASL sasl;
>  #endif
> +
> +    AudioState *audio_state;
>  };
>  
>  typedef struct VncTight {
> diff --git a/monitor/misc.c b/monitor/misc.c
> index e393333a0e..f97810d370 100644
> --- a/monitor/misc.c
> +++ b/monitor/misc.c
> @@ -1148,7 +1148,17 @@ static void hmp_wavcapture(Monitor *mon, const QDict 
> *qdict)
>      int bits = qdict_get_try_int(qdict, "bits", -1);
>      int has_channels = qdict_haskey(qdict, "nchannels");
>      int nchannels = qdict_get_try_int(qdict, "nchannels", -1);
> +    const char *audiodev = qdict_get_try_str(qdict, "audiodev");
>      CaptureState *s;
> +    AudioState *as = NULL;
> +
> +    if (audiodev) {
> +        as = audio_state_by_name(audiodev);
> +        if (!as) {
> +            monitor_printf(mon, "Invalid audiodev specified\n");
> +            return;
> +        }
> +    }

Note for later: if "audiodev" is specified, it must name an existing
AudioState.

>  
>      s = g_malloc0 (sizeof (*s));
>  
> @@ -1156,7 +1166,7 @@ static void hmp_wavcapture(Monitor *mon, const QDict 
> *qdict)
>      bits = has_bits ? bits : 16;
>      nchannels = has_channels ? nchannels : 2;
>  
> -    if (wav_start_capture(NULL, s, path, freq, bits, nchannels)) {
> +    if (wav_start_capture(as, s, path, freq, bits, nchannels)) {
>          monitor_printf(mon, "Failed to add wave capture\n");
>          g_free (s);
>          return;

Note for later: this is the only other failure mode.

> diff --git a/ui/vnc.c b/ui/vnc.c
> index 140f364dda..24f9be5b5d 100644
> --- a/ui/vnc.c
> +++ b/ui/vnc.c
> @@ -1222,7 +1222,7 @@ static void audio_add(VncState *vs)
>      ops.destroy = audio_capture_destroy;
>      ops.capture = audio_capture;
>  
> -    vs->audio_cap = AUD_add_capture(NULL, &vs->as, &ops, vs);
> +    vs->audio_cap = AUD_add_capture(vs->vd->audio_state, &vs->as, &ops, vs);
>      if (!vs->audio_cap) {
>          error_report("Failed to add audio capture");
>      }
> @@ -3369,6 +3369,9 @@ static QemuOptsList qemu_vnc_opts = {
>          },{
>              .name = "non-adaptive",
>              .type = QEMU_OPT_BOOL,
> +        },{
> +            .name = "audiodev",
> +            .type = QEMU_OPT_STRING,
>          },
>          { /* end of list */ }
>      },
> @@ -3806,6 +3809,7 @@ void vnc_display_open(const char *id, Error **errp)
>      const char *saslauthz;
>      int lock_key_sync = 1;
>      int key_delay_ms;
> +    const char *audiodev;
>  
>      if (!vd) {
>          error_setg(errp, "VNC display not active");
> @@ -3991,6 +3995,15 @@ void vnc_display_open(const char *id, Error **errp)
>      }
>      vd->ledstate = 0;
>  
> +    audiodev = qemu_opt_get(opts, "audiodev");
> +    if (audiodev) {
> +        vd->audio_state = audio_state_by_name(audiodev);
> +        if (!vd->audio_state) {
> +            error_setg(errp, "Audiodev '%s' not found", audiodev);
> +            goto fail;
> +        }
> +    }

Note for later: if "audiodev" is specified, it must name an existing
AudioState.

I like this error message better than the one in hmp_wavcapture().  Use
it there, too?

Move it into audio_state_by_name() by giving it an Error **errp
parameter?  Matter of taste, up to you.

> +
>      device_id = qemu_opt_get(opts, "display");
>      if (device_id) {
>          int head = qemu_opt_get_number(opts, "head", 0);
> diff --git a/hmp-commands.hx b/hmp-commands.hx
> index bfa5681dd2..fa7f009268 100644
> --- a/hmp-commands.hx
> +++ b/hmp-commands.hx
> @@ -819,16 +819,19 @@ ETEXI
>  
>      {
>          .name       = "wavcapture",
> -        .args_type  = "path:F,freq:i?,bits:i?,nchannels:i?",
> -        .params     = "path [frequency [bits [channels]]]",
> +        .args_type  = "path:F,freq:i?,bits:i?,nchannels:i?,audiodev:s?",
> +        .params     = "path [frequency [bits [channels [audiodev]]]]",
>          .help       = "capture audio to a wave file (default frequency=44100 
> bits=16 channels=2)",
>          .cmd        = hmp_wavcapture,
>      },
>  STEXI
> -@item wavcapture @var{filename} [@var{frequency} [@var{bits} 
> [@var{channels}]]]
> +@item wavcapture @var{filename} [@var{frequency} [@var{bits} [@var{channels} 
> [@var{audiodev}]]]]
>  @findex wavcapture
> -Capture audio into @var{filename}. Using sample rate @var{frequency}
> -bits per sample @var{bits} and number of channels @var{channels}.
> +Capture audio into @var{filename} from @var{audiodev}, using sample rate
> +@var{frequency} bits per sample @var{bits} and number of channels
> +@var{channels}. When not using an -audiodev argument on command line,
> +@var{audiodev} must be omitted, otherwise is must specify a valid
> +audiodev.

I can see the code for "must specify a valid audiodev" in
hmp_wavcapture().  Where is "must be omitted" checked?

Preexisting: the list "sample rate @var{frequency} bits per sample
@var{bits} and number of channels @var{channels}" lacks a comma after
@var{frequency}, please fix that.  I'd put one after @var{bits} as well,
but that's a matter of taste[*]

The sentence is of the form "if not COND then A else B".  The
less-negated form "if COND then B else A" is commonly easier to read.

Documentation says "from @var{audiodev}".  But when "not using an
-audiodev argument on command line, +@var{audiodev} must be omitted".
Where does it sample from then?  I figure from some default audio
device.  Where is that default audio device explained?  I skimmed the
-audiodev documentation in qemu-options.hx, but couldn't see it there.

Suggest to say "an -audiodev command line option" instead of "an
-audiodev argument on command line".

Double-checking:

* -audiodev is the only way to create an audio backend.

* If the user creates no audio backend, QEMU supplies a default audio
  backend.

Correct?

Other kinds of backends can also be created at run-time with the
monitor.  I'm not asking you provide that for audio.  I'm just wondering
whether it could conceivably be useful.

If yes, you might want to avoid the narrow "if using -audiodev", and
instead say "if the default audio device is in use".

>  
>  Defaults:
>  @itemize @minus
> diff --git a/qemu-options.hx b/qemu-options.hx
> index 9621e934c0..a308e5f5aa 100644
> --- a/qemu-options.hx
> +++ b/qemu-options.hx
> @@ -1978,6 +1978,12 @@ can help the device and guest to keep up and not lose 
> events in case
>  events are arriving in bulk.  Possible causes for the latter are flaky
>  network connections, or scripts for automated testing.
>  
> +@item audiodev=@var{audiodev}
> +
> +Use the specified @var{audiodev} when the VNC client requests audio
> +transmission. When not using an -audiodev argument, this option must
> +be omitted, otherwise is must be present and specify a valid audiodev.
> +
>  @end table
>  ETEXI

Same as for wavcapture, basically.


[*] https://en.wikipedia.org/wiki/Serial_comma