Prosody Audio Video Format (AVF): API: sm_avfplay_start

Prototype Definition

int sm_avfplay_start(struct sm_avfplay_start_parms *avfsp)

Parameters

a structure of the following type:

typedef struct sm_avfplay_start_parms {
	tSMAVFplayId avfplay;					/* in */
	enum kSMAVFOutputType {
		kSMAVFOutputAVFVideo,
		kSMAVFOutputAVFAudio,
		kSMAVFOutputLinearAudio,
	} dest_type;						/* in */
	union {
		struct {
			tSM_INT sampling_rate;			/* in */
			enum kSMAudioDataFormat {
				kSMAudioDataFormatALawPCM,
				kSMAudioDataFormatULawPCM,
				kSMAudioDataFormatAMRNB,
				kSMAudioDataFormat16bit,
				kSMAudioDataFormat8bit,
			} src_type;				/* in */
		} audio;					/* in */
	} u_dest_type;						/* in */
	tSM_INT hbuf_size;					/* in */
	tSM_INT test_mode;					/* in */
} SM_AVFPLAY_START_PARMS;

Description

Starts the necessary tasks on the module for playback of AVF-encapsulated video or audio.

Note that, unlike most tasks, an AVF player can output different types of data - e.g. AVF AMR-NB audio stream, AVF H.263 video stream, etc. - dependant on how it is started. It is the application writer's responsibility to ensure that any task (e.g. VMP[tx]) connected to the AVF player's datafeed is able to process this data.

Note: The union in in the above struct is used to allow future expansion.

Fields

avfplay

A tSMAVFplayId that has been prevously created by a call to sm_avfplay_create().

dest_type

The type of data to output on the datafeed. One of these values:

kSMAVFOutputAVFVideo: Output raw AVF-encapsulated video frames. The AVF player does not modify or interpret the media data within these frames.
kSMAVFOutputAVFAudio: Output raw AVF-encapsulated audio frames. The AVF player does not modify or interpret the media data within these frames.
kSMAVFOutputLinearAudio: Output linear audio, converting the supplied AVF-encapsulated audio frames' payload using the audio decoder specified in the src_type field.

u_dest_type

audio

This struct is valid only if dest_type is kSMAVFOutputAVFAudio or kSMAVFOutputLinearAudio

sampling_rate

The output sampling rate in Hz. For example, 8000 for narrowband audio. If set to 0, a value of 8000 is assumed.

src_type

The audio encoding of the AVF-encapsulated source data. One of these values:

kSMAudioDataFormatALawPCM: G.711 A-law. This uses 8 bits per sample.
kSMAudioDataFormatULawPCM: G.711 mu-law. This uses 8 bits per sample.
kSMAudioDataFormatAMRNB: AMR-NB. The sampling rate must be 8000Hz.
kSMAudioDataFormat16bit: 16-bit linear coding, where each sample is a signed value (-32768 to 32767). The first octet of each sample is the less significant one.
kSMAudioDataFormat8bit: 8-bit unsigned linear coding, where each sample is an unsigned value (0 to 255). This is Microsoft's 8-bit format.

hbuf_size

This must be set to the desired size of the playback's buffer on the module in bytes. For audio replays 8192 is generally a suitable value. For video replays the value depends on the video content but MUST be comfortably larger than the largest AVF frame to be replayed. If set to 0, for dest_type kSMAVFOutputAVFAudio the assumed size is 8192, and for dest_type kSMAVFOutputAVFVideo the assumed size is 32768. This value is ignored if dest_type is kSMAVFOutputLinearAudio and, in this case, a default buffer size is used as for regular audio playback.

test_mode

For Aculab use only: sets the test mode. Must be set to 0 for normal operation.

Returns

0 if call completed successfully, otherwise a standard error such as:

ERR_SM_DEVERR - device error

This function is part of the Prosody Audio Video Format (AVF) API.