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* Copyright (c) 2021, Alliance for Open Media. All rights reserved
* This source code is subject to the terms of the BSD 3-Clause Clear License and the
* Alliance for Open Media Patent License 1.0. If the BSD 3-Clause Clear License was
* not distributed with this source code in the LICENSE file, you can obtain it
* at If the Alliance for Open Media Patent
* License 1.0 was not distributed with this source code in the PATENTS file, you
* can obtain it at
#include "libyuv/basic_types.h"
#ifdef __cplusplus
// NOTE: For a simplified public API use convert.h MJPGToI420().
struct jpeg_common_struct;
struct jpeg_decompress_struct;
struct jpeg_source_mgr;
namespace libyuv {
#ifdef __cplusplus
extern "C" {
LIBYUV_BOOL ValidateJpeg(const uint8* sample, size_t sample_size);
#ifdef __cplusplus
} // extern "C"
static const uint32 kUnknownDataSize = 0xFFFFFFFF;
enum JpegSubsamplingType {
struct Buffer {
const uint8* data;
int len;
struct BufferVector {
Buffer* buffers;
int len;
int pos;
struct SetJmpErrorMgr;
// MJPEG ("Motion JPEG") is a pseudo-standard video codec where the frames are
// simply independent JPEG images with a fixed huffman table (which is omitted).
// It is rarely used in video transmission, but is common as a camera capture
// format, especially in Logitech devices. This class implements a decoder for
// MJPEG frames.
// See
class LIBYUV_API MJpegDecoder {
typedef void (*CallbackFunction)(void* opaque,
const uint8* const* data,
const int* strides,
int rows);
static const int kColorSpaceUnknown;
static const int kColorSpaceGrayscale;
static const int kColorSpaceRgb;
static const int kColorSpaceYCbCr;
static const int kColorSpaceCMYK;
static const int kColorSpaceYCCK;
// Loads a new frame, reads its headers, and determines the uncompressed
// image format.
// Returns LIBYUV_TRUE if image looks valid and format is supported.
// If return value is LIBYUV_TRUE, then the values for all the following
// getters are populated.
// src_len is the size of the compressed mjpeg frame in bytes.
LIBYUV_BOOL LoadFrame(const uint8* src, size_t src_len);
// Returns width of the last loaded frame in pixels.
int GetWidth();
// Returns height of the last loaded frame in pixels.
int GetHeight();
// Returns format of the last loaded frame. The return value is one of the
// kColorSpace* constants.
int GetColorSpace();
// Number of color components in the color space.
int GetNumComponents();
// Sample factors of the n-th component.
int GetHorizSampFactor(int component);
int GetVertSampFactor(int component);
int GetHorizSubSampFactor(int component);
int GetVertSubSampFactor(int component);
// Public for testability.
int GetImageScanlinesPerImcuRow();
// Public for testability.
int GetComponentScanlinesPerImcuRow(int component);
// Width of a component in bytes.
int GetComponentWidth(int component);
// Height of a component.
int GetComponentHeight(int component);
// Width of a component in bytes with padding for DCTSIZE. Public for testing.
int GetComponentStride(int component);
// Size of a component in bytes.
int GetComponentSize(int component);
// Call this after LoadFrame() if you decide you don't want to decode it
// after all.
LIBYUV_BOOL UnloadFrame();
// Decodes the entire image into a one-buffer-per-color-component format.
// dst_width must match exactly. dst_height must be <= to image height; if
// less, the image is cropped. "planes" must have size equal to at least
// GetNumComponents() and they must point to non-overlapping buffers of size
// at least GetComponentSize(i). The pointers in planes are incremented
// to point to after the end of the written data.
// TODO(fbarchard): Add dst_x, dst_y to allow specific rect to be decoded.
LIBYUV_BOOL DecodeToBuffers(uint8** planes, int dst_width, int dst_height);
// Decodes the entire image and passes the data via repeated calls to a
// callback function. Each call will get the data for a whole number of
// image scanlines.
// TODO(fbarchard): Add dst_x, dst_y to allow specific rect to be decoded.
LIBYUV_BOOL DecodeToCallback(CallbackFunction fn, void* opaque,
int dst_width, int dst_height);
// The helper function which recognizes the jpeg sub-sampling type.
static JpegSubsamplingType JpegSubsamplingTypeHelper(
int* subsample_x, int* subsample_y, int number_of_components);
void AllocOutputBuffers(int num_outbufs);
void DestroyOutputBuffers();
LIBYUV_BOOL StartDecode();
LIBYUV_BOOL FinishDecode();
void SetScanlinePointers(uint8** data);
LIBYUV_BOOL DecodeImcuRow();
int GetComponentScanlinePadding(int component);
// A buffer holding the input data for a frame.
Buffer buf_;
BufferVector buf_vec_;
jpeg_decompress_struct* decompress_struct_;
jpeg_source_mgr* source_mgr_;
SetJmpErrorMgr* error_mgr_;
// LIBYUV_TRUE iff at least one component has scanline padding. (i.e.,
// GetComponentScanlinePadding() != 0.)
LIBYUV_BOOL has_scanline_padding_;
// Temporaries used to point to scanline outputs.
int num_outbufs_; // Outermost size of all arrays below.
uint8*** scanlines_;
int* scanlines_sizes_;
// Temporary buffer used for decoding when we can't decode directly to the
// output buffers. Large enough for just one iMCU row.
uint8** databuf_;
int* databuf_strides_;
} // namespace libyuv
#endif // __cplusplus