libavcodec/wmadec.c File Reference

WMA compatible decoder. More...

#include "avcodec.h"
#include "wma.h"
#include <assert.h>

Go to the source code of this file.

Defines
#define	EXPVLCBITS   8
#define	EXPMAX   ((19+EXPVLCBITS-1)/EXPVLCBITS)
#define	HGAINVLCBITS   9
#define	HGAINMAX   ((13+HGAINVLCBITS-1)/HGAINVLCBITS)
Functions
static void	wma_lsp_to_curve_init (WMACodecContext *s, int frame_len)
static int	wma_decode_init (AVCodecContext *avctx)
static float	pow_m1_4 (WMACodecContext *s, float x)
	compute x^-0.25 with an exponent and mantissa table.
static void	wma_lsp_to_curve (WMACodecContext *s, float *out, float *val_max_ptr, int n, float *lsp)
	NOTE: We use the same code as Vorbis here.
static void	decode_exp_lsp (WMACodecContext *s, int ch)
	decode exponents coded with LSP coefficients (same idea as Vorbis)
static int	decode_exp_vlc (WMACodecContext *s, int ch)
	decode exponents coded with VLC codes
static void	wma_window (WMACodecContext *s, float *out)
	Apply MDCT window and add into output.
static int	wma_decode_block (WMACodecContext *s)
static int	wma_decode_frame (WMACodecContext *s, int16_t *samples)
static int	wma_decode_superframe (AVCodecContext *avctx, void *data, int *got_frame_ptr, AVPacket *avpkt)
static av_cold void	flush (AVCodecContext *avctx)
Variables
static const float	pow_tab []
	pow(10, i / 16.0) for i in -60.

---

Detailed Description

WMA compatible decoder.

This decoder handles Microsoft Windows Media Audio data, versions 1 & 2. WMA v1 is identified by audio format 0x160 in Microsoft media files (ASF/AVI/WAV). WMA v2 is identified by audio format 0x161.

To use this decoder, a calling application must supply the extra data bytes provided with the WMA data. These are the extra, codec-specific bytes at the end of a WAVEFORMATEX data structure. Transmit these bytes to the decoder using the extradata[_size] fields in AVCodecContext. There should be 4 extra bytes for v1 data and 6 extra bytes for v2 data.

Definition in file wmadec.c.

---

Define Documentation

#define EXPMAX   ((19+EXPVLCBITS-1)/EXPVLCBITS)

Definition at line 43 of file wmadec.c.

Referenced by decode_exp_vlc().

#define EXPVLCBITS   8

Definition at line 42 of file wmadec.c.

Referenced by decode_exp_vlc(), and wma_decode_init().

#define HGAINMAX   ((13+HGAINVLCBITS-1)/HGAINVLCBITS)

Definition at line 46 of file wmadec.c.

Referenced by wma_decode_block().

#define HGAINVLCBITS   9

Definition at line 45 of file wmadec.c.

Referenced by wma_decode_block(), and wma_decode_init().

---

Function Documentation

static void decode_exp_lsp	(	WMACodecContext *	s,
		int	ch
	)			[static]

decode exponents coded with LSP coefficients (same idea as Vorbis)

Definition at line 228 of file wmadec.c.

Referenced by wma_decode_block().

static int decode_exp_vlc	(	WMACodecContext *	s,
		int	ch
	)			[static]

decode exponents coded with VLC codes

Definition at line 330 of file wmadec.c.

Referenced by wma_decode_block().

static av_cold void flush

(

AVCodecContext *

avctx

)

[static]

Definition at line 944 of file wmadec.c.

static float pow_m1_4	(	WMACodecContext *	s,
		float	x
	)			[inline, static]

compute x^-0.25 with an exponent and mantissa table.

We use linear interpolation to reduce the mantissa table size at a small speed expense (linear interpolation approximately doubles the number of bits of precision).

Definition at line 147 of file wmadec.c.

Referenced by wma_lsp_to_curve().

static int wma_decode_block

(

WMACodecContext *

s

)

[static]

Returns:

0 if OK. 1 if last block of frame. return -1 if unrecorrable error.

Definition at line 446 of file wmadec.c.

Referenced by wma_decode_frame().

static int wma_decode_frame	(	WMACodecContext *	s,
		int16_t *	samples
	)			[static]

Definition at line 779 of file wmadec.c.

Referenced by wma_decode_superframe().

static int wma_decode_init

(

AVCodecContext *

avctx

)

[static]

Definition at line 82 of file wmadec.c.

static int wma_decode_superframe	(	AVCodecContext *	avctx,
		void *	data,
		int *	got_frame_ptr,
		AVPacket *	avpkt
	)			[static]

Definition at line 816 of file wmadec.c.

static void wma_lsp_to_curve	(	WMACodecContext *	s,
		float *	out,
		float *	val_max_ptr,
		int	n,
		float *	lsp
	)			[static]

NOTE: We use the same code as Vorbis here.

Todo:

optimize it further with SSE/3Dnow

Definition at line 198 of file wmadec.c.

Referenced by decode_exp_lsp().

static void wma_lsp_to_curve_init	(	WMACodecContext *	s,
		int	frame_len
	)			[static]

Definition at line 166 of file wmadec.c.

Referenced by wma_decode_init().

static void wma_window	(	WMACodecContext *	s,
		float *	out
	)			[static]

Apply MDCT window and add into output.

We ensure that when the windows overlap their squared sum is always 1 (MDCT reconstruction rule).

Definition at line 394 of file wmadec.c.

Referenced by wma_decode_block().

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Variable Documentation

const float pow_tab[] [static]

pow(10, i / 16.0) for i in -60.

.95

Definition at line 246 of file wmadec.c.