vp8_dec.h - mozsearch

Enable keyboard shortcuts

// Copyright 2010 Google Inc. All Rights Reserved.

//

// Use of this source code is governed by a BSD-style license

// that can be found in the COPYING file in the root of the source

// tree. An additional intellectual property rights grant can be found

// in the file PATENTS. All contributing project authors may

// be found in the AUTHORS file in the root of the source tree.

// -----------------------------------------------------------------------------

//

//  Low-level API for VP8 decoder

//

// Author: Skal (pascal.massimino@gmail.com)

#ifndef WEBP_DEC_VP8_DEC_H_

#define WEBP_DEC_VP8_DEC_H_

#include "src/webp/decode.h"

#include "src/webp/types.h"

#ifdef __cplusplus

extern "C" {

#endif

//------------------------------------------------------------------------------

// Lower-level API

//

// These functions provide fine-grained control of the decoding process.

// The call flow should resemble:

//

//   VP8Io io;

//   VP8InitIo(&io);

//   io.data = data;

//   io.data_size = size;

//   /* customize io's functions (setup()/put()/teardown()) if needed. */

//

//   VP8Decoder* dec = VP8New();

//   int ok = VP8Decode(dec, &io);

//   if (!ok) printf("Error: %s\n", VP8StatusMessage(dec));

//   VP8Delete(dec);

//   return ok;

// Input / Output

typedef struct VP8Io VP8Io;

typedef int (*VP8IoPutHook)(const VP8Io* io);

typedef int (*VP8IoSetupHook)(VP8Io* io);

typedef void (*VP8IoTeardownHook)(const VP8Io* io);

struct VP8Io {

  // set by VP8GetHeaders()

  int width, height;         // picture dimensions, in pixels (invariable).

                             // These are the original, uncropped dimensions.

                             // The actual area passed to put() is stored

                             // in mb_w / mb_h fields.

  // set before calling put()

  int mb_y;                  // position of the current rows (in pixels)

  int mb_w;                  // number of columns in the sample

  int mb_h;                  // number of rows in the sample

  const uint8_t* y, *u, *v;  // rows to copy (in yuv420 format)

  int y_stride;              // row stride for luma

  int uv_stride;             // row stride for chroma

  void* opaque;              // user data

  // called when fresh samples are available. Currently, samples are in

  // YUV420 format, and can be up to width x 24 in size (depending on the

  // in-loop filtering level, e.g.). Should return false in case of error

  // or abort request. The actual size of the area to update is mb_w x mb_h

  // in size, taking cropping into account.

  VP8IoPutHook put;

  // called just before starting to decode the blocks.

  // Must return false in case of setup error, true otherwise. If false is

  // returned, teardown() will NOT be called. But if the setup succeeded

  // and true is returned, then teardown() will always be called afterward.

  VP8IoSetupHook setup;

  // Called just after block decoding is finished (or when an error occurred

  // during put()). Is NOT called if setup() failed.

  VP8IoTeardownHook teardown;

  // this is a recommendation for the user-side yuv->rgb converter. This flag

  // is set when calling setup() hook and can be overwritten by it. It then

  // can be taken into consideration during the put() method.

  int fancy_upsampling;

  // Input buffer.

  size_t data_size;

  const uint8_t* data;

  // If true, in-loop filtering will not be performed even if present in the

  // bitstream. Switching off filtering may speed up decoding at the expense

  // of more visible blocking. Note that output will also be non-compliant

  // with the VP8 specifications.

  int bypass_filtering;

  // Cropping parameters.

  int use_cropping;

  int crop_left, crop_right, crop_top, crop_bottom;

  // Scaling parameters.

  int use_scaling;

  int scaled_width, scaled_height;

  // If non NULL, pointer to the alpha data (if present) corresponding to the

  // start of the current row (That is: it is pre-offset by mb_y and takes

  // cropping into account).

  const uint8_t* a;

};

// Internal, version-checked, entry point

WEBP_NODISCARD int VP8InitIoInternal(VP8Io* const, int);

// Set the custom IO function pointers and user-data. The setter for IO hooks

// should be called before initiating incremental decoding. Returns true if

// WebPIDecoder object is successfully modified, false otherwise.

WEBP_NODISCARD int WebPISetIOHooks(WebPIDecoder* const idec, VP8IoPutHook put,

                                   VP8IoSetupHook setup,

                                   VP8IoTeardownHook teardown, void* user_data);

// Main decoding object. This is an opaque structure.

typedef struct VP8Decoder VP8Decoder;

// Create a new decoder object.

VP8Decoder* VP8New(void);

// Must be called to make sure 'io' is initialized properly.

// Returns false in case of version mismatch. Upon such failure, no other

// decoding function should be called (VP8Decode, VP8GetHeaders, ...)

WEBP_NODISCARD static WEBP_INLINE int VP8InitIo(VP8Io* const io) {

  return VP8InitIoInternal(io, WEBP_DECODER_ABI_VERSION);

// Decode the VP8 frame header. Returns true if ok.

// Note: 'io->data' must be pointing to the start of the VP8 frame header.

WEBP_NODISCARD int VP8GetHeaders(VP8Decoder* const dec, VP8Io* const io);

// Decode a picture. Will call VP8GetHeaders() if it wasn't done already.

// Returns false in case of error.

WEBP_NODISCARD int VP8Decode(VP8Decoder* const dec, VP8Io* const io);

// Return current status of the decoder:

VP8StatusCode VP8Status(VP8Decoder* const dec);

// return readable string corresponding to the last status.

const char* VP8StatusMessage(VP8Decoder* const dec);

// Resets the decoder in its initial state, reclaiming memory.

// Not a mandatory call between calls to VP8Decode().

void VP8Clear(VP8Decoder* const dec);

// Destroy the decoder object.

void VP8Delete(VP8Decoder* const dec);

//------------------------------------------------------------------------------

// Miscellaneous VP8/VP8L bitstream probing functions.

// Returns true if the next 3 bytes in data contain the VP8 signature.

WEBP_EXTERN int VP8CheckSignature(const uint8_t* const data, size_t data_size);

// Validates the VP8 data-header and retrieves basic header information viz

// width and height. Returns 0 in case of formatting error. *width/*height

// can be passed NULL.

WEBP_EXTERN int VP8GetInfo(

    const uint8_t* data,

    size_t data_size,    // data available so far

    size_t chunk_size,   // total data size expected in the chunk

    int* const width, int* const height);

// Returns true if the next byte(s) in data is a VP8L signature.

WEBP_EXTERN int VP8LCheckSignature(const uint8_t* const data, size_t size);

// Validates the VP8L data-header and retrieves basic header information viz

// width, height and alpha. Returns 0 in case of formatting error.

// width/height/has_alpha can be passed NULL.

WEBP_EXTERN int VP8LGetInfo(

    const uint8_t* data, size_t data_size,  // data available so far

    int* const width, int* const height, int* const has_alpha);

#ifdef __cplusplus

}    // extern "C"

#endif

#endif  // WEBP_DEC_VP8_DEC_H_