The VideoLAN Forums

Posted: **23 Feb 2019 10:02**

I'm looking at this API function:

/**
 * Set current audio channel.
 *
 * \param p_mi media player
 * \param channel the audio channel, \see libvlc_audio_output_channel_t
 * \return 0 on success, -1 on error
 */
LIBVLC_API int libvlc_audio_set_channel( libvlc_media_player_t *p_mi, int channel );

For the channel values, it refers to libvlc_media_player.h which declares this:

Code: Select all

typedef enum libvlc_audio_output_channel_t {
    libvlc_AudioChannel_Error   = -1,
    libvlc_AudioChannel_Stereo  =  1,
    libvlc_AudioChannel_RStereo =  2,
    libvlc_AudioChannel_Left    =  3,
    libvlc_AudioChannel_Right   =  4,
    libvlc_AudioChannel_Dolbys  =  5
} libvlc_audio_output_channel_t;

vlc_aout.h declares this:

Code: Select all

/* Values used for the audio-channels object variable */
#define AOUT_VAR_CHAN_UNSET         0 /* must be zero */
#define AOUT_VAR_CHAN_STEREO        1
#define AOUT_VAR_CHAN_RSTEREO       2
#define AOUT_VAR_CHAN_LEFT          3
#define AOUT_VAR_CHAN_RIGHT         4
#define AOUT_VAR_CHAN_DOLBYS        5
#define AOUT_VAR_CHAN_HEADPHONES    6
#define AOUT_VAR_CHAN_MONO          7

Are the "headphones" and "mono" values, and I suppose "unset" too, supposed to be available via the API on the libvlc_audio_output_channel_t enum?

Posted: **25 Feb 2019 03:46**

What are you trying to achieve?

Looking for this?

Code: Select all

typedef enum libvlc_audio_output_device_types_t {
    libvlc_AudioOutputDevice_Error  = -1,
    libvlc_AudioOutputDevice_Mono   =  1,
    libvlc_AudioOutputDevice_Stereo =  2,
    libvlc_AudioOutputDevice_2F2R   =  4,
    libvlc_AudioOutputDevice_3F2R   =  5,
    libvlc_AudioOutputDevice_5_1    =  6,
    libvlc_AudioOutputDevice_6_1    =  7,
    libvlc_AudioOutputDevice_7_1    =  8,
    libvlc_AudioOutputDevice_SPDIF  = 10
} libvlc_audio_output_device_types_t;

Posted: **25 Feb 2019 09:51**

No, there is an existing API function, libvlc_audio_set_channel, that lets you set the stereo mode using the values in libvlc_audio_output_channel_t.

This is not the same API that uses the libvlc_audio_output_device_types_t you mention - that API is libvlc_audio_output_device_enum or libvlc_audio_output_device_list_get.

My question is if the public API, libvlc_audio_output_channel_t, currently defines all the allowable values or if it is missing some of them from vlc_aout.h, i.e. headphones and mono. Since it's an enum I can just pass the int value for those "missing" values, so it really isn't a big deal, but is it correct.

I don't think setting the audio channel (I think this is the "stereo-mode" variable in the VLC sources) is the same as setting the device type - there are separate API's for those two things.

Posted: **25 Feb 2019 11:34**

My question is if the public API, libvlc_audio_output_channel_t, currently defines all the allowable values or if it is missing some of them from vlc_aout.h

I don't know.

Maybe related: Are you aware of the following libvlc options https://wiki.videolan.org/VLC_command-line_help/

Code: Select all

--stereo-mode={0 (Unset), 1 (Stereo), 2 (Reverse stereo), 3 (Left), 4 (Right), 5 (Dolby Surround), 6 (Headphones)} 
                                 Stereo audio output mode

Posted: **25 Feb 2019 12:35**

It's the headphones one I was most interested in. It seems to me it should be OK to use those values.

This is not a big problem really, I just like to be thorough when I implement the API.

Thank you for your replies.

Posted: **10 Mar 2019 11:41**

I opened a bugreport https://trac.videolan.org/vlc/ticket/22013

The VideoLAN Forums

libvlc_audio_set_channel and libvlc_audio_output_channel_t values

libvlc_audio_set_channel and libvlc_audio_output_channel_t values

Re: libvlc_audio_set_channel and libvlc_audio_output_channel_t values

Re: libvlc_audio_set_channel and libvlc_audio_output_channel_t values

Re: libvlc_audio_set_channel and libvlc_audio_output_channel_t values

Re: libvlc_audio_set_channel and libvlc_audio_output_channel_t values

Re: libvlc_audio_set_channel and libvlc_audio_output_channel_t values