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北京网站建设哪便宜,温州seo服务,wordpress适合做博客的主题,有创意的广告本章主要介绍FFmpeg基础组件AVFrame. 文章目录 1.结构体成员2.成员函数AVFrame Host内存的获取 av_frame_get_bufferAVFrame device内存获取av_hwframe_get_buffer#xff08;#xff09; 1.结构体成员 我们把所有的代码先粘贴上来#xff0c;在后边一个一个解释。 typede…本章主要介绍FFmpeg基础组件AVFrame. 文章目录 1.结构体成员2.成员函数AVFrame Host内存的获取 av_frame_get_bufferAVFrame device内存获取av_hwframe_get_buffer 1.结构体成员 我们把所有的代码先粘贴上来在后边一个一个解释。 typedef struct AVFrame { #define AV_NUM_DATA_POINTERS 8/*** pointer to the picture/channel planes.* This might be different from the first allocated byte. For video,* it could even point to the end of the image data.** All pointers in data and extended_data must point into one of the* AVBufferRef in buf or extended_buf.** Some decoders access areas outside 0,0 - width,height, please* see avcodec_align_dimensions2(). Some filters and swscale can read* up to 16 bytes beyond the planes, if these filters are to be used,* then 16 extra bytes must be allocated.** NOTE: Pointers not needed by the format MUST be set to NULL.** attention In case of video, the data[] pointers can point to the* end of image data in order to reverse line order, when used in* combination with negative values in the linesize[] array.*/uint8_t data[AV_NUM_DATA_POINTERS];/** For video, a positive or negative value, which is typically indicating* the size in bytes of each picture line, but it can also be:* - the negative byte size of lines for vertical flipping* (with data[n] pointing to the end of the data* - a positive or negative multiple of the byte size as for accessing* even and odd fields of a frame (possibly flipped)** For audio, only linesize[0] may be set. For planar audio, each channel* plane must be the same size.** For video the linesizes should be multiples of the CPUs alignment* preference, this is 16 or 32 for modern desktop CPUs.* Some code requires such alignment other code can be slower without* correct alignment, for yet other it makes no difference.** note The linesize may be larger than the size of usable data – there* may be extra padding present for performance reasons.** attention In case of video, line size values can be negative to achieve* a vertically inverted iteration over image lines./int linesize[AV_NUM_DATA_POINTERS];/** pointers to the data planes/channels.** For video, this should simply point to data[].** For planar audio, each channel has a separate data pointer, and* linesize[0] contains the size of each channel buffer.* For packed audio, there is just one data pointer, and linesize[0]* contains the total size of the buffer for all channels.** Note: Both data and extended_data should always be set in a valid frame,* but for planar audio with more channels that can fit in data,* extended_data must be used in order to access all channels./uint8_t extended_data;/ name Video dimensions* Video frames only. The coded dimensions (in pixels) of the video frame,* i.e. the size of the rectangle that contains some well-defined values.** note The part of the frame intended for display/presentation is further* restricted by the ref cropping Cropping rectangle.* {/int width, height;/** }//** number of audio samples (per channel) described by this frame/int nb_samples;/** format of the frame, -1 if unknown or unset* Values correspond to enum AVPixelFormat for video frames,* enum AVSampleFormat for audio)/int format;/** 1 - keyframe, 0- not/int key_frame;/** Picture type of the frame./enum AVPictureType pict_type;/** Sample aspect ratio for the video frame, 0/1 if unknown/unspecified./AVRational sample_aspect_ratio;/** Presentation timestamp in time_base units (time when frame should be shown to user)./int64_t pts;/** DTS copied from the AVPacket that triggered returning this frame. (if frame threading isnt used)* This is also the Presentation time of this AVFrame calculated from* only AVPacket.dts values without pts values./int64_t pkt_dts;/** Time base for the timestamps in this frame.* In the future, this field may be set on frames output by decoders or* filters, but its value will be by default ignored on input to encoders* or filters./AVRational time_base;/** picture number in bitstream order/int coded_picture_number;/** picture number in display order/int display_picture_number;/** quality (between 1 (good) and FF_LAMBDA_MAX (bad))/int quality;/** for some private data of the user*/void opaque;/** When decoding, this signals how much the picture must be delayed.* extra_delay repeat_pict / (2fps)/int repeat_pict;/*** The content of the picture is interlaced./int interlaced_frame;/** If the content is interlaced, is top field displayed first./int top_field_first;/** Tell user application that palette has changed from previous frame./int palette_has_changed;/** reordered opaque 64 bits (generally an integer or a double precision float* PTS but can be anything).* The user sets AVCodecContext.reordered_opaque to represent the input at* that time,* the decoder reorders values as needed and sets AVFrame.reordered_opaque* to exactly one of the values provided by the user through AVCodecContext.reordered_opaque/int64_t reordered_opaque;/** Sample rate of the audio data./int sample_rate;/** Channel layout of the audio data./uint64_t channel_layout;/** AVBuffer references backing the data for this frame. All the pointers in* data and extended_data must point inside one of the buffers in buf or* extended_buf. This array must be filled contiguously – if buf[i] is* non-NULL then buf[j] must also be non-NULL for all j i.** There may be at most one AVBuffer per data plane, so for video this array* always contains all the references. For planar audio with more than* AV_NUM_DATA_POINTERS channels, there may be more buffers than can fit in* this array. Then the extra AVBufferRef pointers are stored in the* extended_buf array.*/AVBufferRef buf[AV_NUM_DATA_POINTERS];/** For planar audio which requires more than AV_NUM_DATA_POINTERS* AVBufferRef pointers, this array will hold all the references which* cannot fit into AVFrame.buf.** Note that this is different from AVFrame.extended_data, which always* contains all the pointers. This array only contains the extra pointers,* which cannot fit into AVFrame.buf.** This array is always allocated using av_malloc() by whoever constructs* the frame. It is freed in av_frame_unref()./AVBufferRef extended_buf;/ Number of elements in extended_buf./int nb_extended_buf;AVFrameSideData side_data;int nb_side_data;/ defgroup lavu_frame_flags AV_FRAME_FLAGS* ingroup lavu_frame* Flags describing additional frame properties.** {//** The frame data may be corrupted, e.g. due to decoding errors./ #define AV_FRAME_FLAG_CORRUPT (1 0) /** A flag to mark the frames which need to be decoded, but shouldnt be output./ #define AV_FRAME_FLAG_DISCARD (1 2) /** }//** Frame flags, a combination of ref lavu_frame_flags/int flags;/** MPEG vs JPEG YUV range.* - encoding: Set by user* - decoding: Set by libavcodec/enum AVColorRange color_range;enum AVColorPrimaries color_primaries;enum AVColorTransferCharacteristic color_trc;/** YUV colorspace type.* - encoding: Set by user* - decoding: Set by libavcodec/enum AVColorSpace colorspace;enum AVChromaLocation chroma_location;/** frame timestamp estimated using various heuristics, in stream time base* - encoding: unused* - decoding: set by libavcodec, read by user./int64_t best_effort_timestamp;/** reordered pos from the last AVPacket that has been input into the decoder* - encoding: unused* - decoding: Read by user./int64_t pkt_pos;/** duration of the corresponding packet, expressed in* AVStream-time_base units, 0 if unknown.* - encoding: unused* - decoding: Read by user./int64_t pkt_duration;/** metadata.* - encoding: Set by user.* - decoding: Set by libavcodec.*/AVDictionary metadata;/** decode error flags of the frame, set to a combination of* FF_DECODE_ERROR_xxx flags if the decoder produced a frame, but there* were errors during the decoding.* - encoding: unused* - decoding: set by libavcodec, read by user./int decode_error_flags; #define FF_DECODE_ERROR_INVALID_BITSTREAM 1 #define FF_DECODE_ERROR_MISSING_REFERENCE 2 #define FF_DECODE_ERROR_CONCEALMENT_ACTIVE 4 #define FF_DECODE_ERROR_DECODE_SLICES 8/** number of audio channels, only used for audio.* - encoding: unused* - decoding: Read by user./int channels;/** size of the corresponding packet containing the compressed* frame.* It is set to a negative value if unknown.* - encoding: unused* - decoding: set by libavcodec, read by user./int pkt_size;/** For hwaccel-format frames, this should be a reference to the* AVHWFramesContext describing the frame.*/AVBufferRef hw_frames_ctx;/** AVBufferRef for free use by the API user. FFmpeg will never check the* contents of the buffer ref. FFmpeg calls av_buffer_unref() on it when* the frame is unreferenced. av_frame_copy_props() calls create a new* reference with av_buffer_ref() for the target frames opaque_ref field.** This is unrelated to the opaque field, although it serves a similar* purpose.*/AVBufferRef opaque_ref;/** anchor cropping* name Cropping* Video frames only. The number of pixels to discard from the the* top/bottom/left/right border of the frame to obtain the sub-rectangle of* the frame intended for presentation.* {/size_t crop_top;size_t crop_bottom;size_t crop_left;size_t crop_right;/** }//** AVBufferRef for internal use by a single libav* library.* Must not be used to transfer data between libraries.* Has to be NULL when ownership of the frame leaves the respective library.** Code outside the FFmpeg libs should never check or change the contents of the buffer ref.** FFmpeg calls av_buffer_unref() on it when the frame is unreferenced.* av_frame_copy_props() calls create a new reference with av_buffer_ref()* for the target frames private_ref field.*/AVBufferRef *private_ref; } AVFrame;AVFrame中核心成员我们常用的就是下面几个 typedef struct AVFrame { …uint8_t *data[AV_NUM_DATA_POINTERS]int linesize[AV_NUM_DATA_POINTERS];uint8_t **extended_data;uint8_t extended_data;int width, height;int format;int key_frame;int64_t pts;int64_t pkt_dts;AVRational time_base;AVBufferRef *buf[AV_NUM_DATA_POINTERS]; … }这个结构体主要保存解码后的YUV数据特别注意的是AVBufferRef *buf[AV_NUM_DATA_POINTERS];这个成员因为它用来进行分配内存的释放。 其实在很多地方用到了AVBufferRef 原理就是其中内部使用了一个引用当引用为1的时候就把内部指向的memory释放掉。 /* A reference counted buffer type. It is opaque and is meant to be used through* references (AVBufferRef)./ typedef struct AVBuffer AVBuffer;/** A reference to a data buffer.** The size of this struct is not a part of the public ABI and it is not meant* to be allocated directly.*/ typedef struct AVBufferRef {AVBuffer buffer;/** The data buffer. It is considered writable if and only if* this is the only reference to the buffer, in which case* av_buffer_is_writable() returns 1.*/uint8_t data;/** Size of data in bytes.*/size_t size; } AVBufferRef;其中data就是yuv数据size就是数据大小我们看到里面的AVBuffer 其详细结构如下其中refcount就是引用数量free就是释放函数 struct AVBuffer {uint8_t *data; /** data described by this buffer */size_t size; /** size of data in bytes //** number of existing AVBufferRef instances referring to this buffer/atomic_uint refcount;/** a callback for freeing the data*/void (*free)(void *opaque, uint8_t data);/** an opaque pointer, to be used by the freeing callback*/void opaque;/** A combination of AV_BUFFERFLAG/int flags;/* A combination of BUFFERFLAG/int flags_internal; };关于这一块智能引用其提供了一些函数族 /* Allocate an AVBuffer of the given size using av_malloc().** return an AVBufferRef of given size or NULL when out of memory*/ AVBufferRef av_buffer_alloc(size_t size);/** Same as av_buffer_alloc(), except the returned buffer will be initialized* to zero.*/ AVBufferRef av_buffer_allocz(size_t size);/** Create an AVBuffer from an existing array.** If this function is successful, data is owned by the AVBuffer. The caller may* only access data through the returned AVBufferRef and references derived from* it.* If this function fails, data is left untouched.* param data data array* param size size of data in bytes* param free a callback for freeing this buffers data* param opaque parameter to be got for processing or passed to free* param flags a combination of AV_BUFFERFLAG*** return an AVBufferRef referring to data on success, NULL on failure.*/ AVBufferRef *av_buffer_create(uint8_t *data, size_t size,void (*free)(void *opaque, uint8_t *data),void opaque, int flags);/** Default free callback, which calls av_free() on the buffer data.* This function is meant to be passed to av_buffer_create(), not called* directly.*/ void av_buffer_default_free(void *opaque, uint8_t data);/** Create a new reference to an AVBuffer.** return a new AVBufferRef referring to the same AVBuffer as buf or NULL on* failure.*/ AVBufferRef *av_buffer_ref(const AVBufferRef buf);/** Free a given reference and automatically free the buffer if there are no more* references to it.** param buf the reference to be freed. The pointer is set to NULL on return./ void av_buffer_unref(AVBufferRef buf);/ return 1 if the caller may write to the data referred to by buf (which is* true if and only if buf is the only reference to the underlying AVBuffer).* Return 0 otherwise.* A positive answer is valid until av_buffer_ref() is called on buf.*/ int av_buffer_is_writable(const AVBufferRef buf);/** return the opaque parameter set by av_buffer_create.*/ void *av_buffer_get_opaque(const AVBufferRef *buf);int av_buffer_get_ref_count(const AVBufferRef *buf);这些函数族用户是用不到的一般在ffmpeg内部模块中使用到。比如AVFrame函数族中。 其余根据字面意思很好理解。其中linesize表示每个plane的步长。 比如YUV420的数其数据长度大小为 if (frame-pixel_format TOPSCODEC_PIX_FMT_I420 ||frame-pixel_format TOPSCODEC_PIX_FMT_NV12 ||frame-pixel_format TOPSCODEC_PIX_FMT_NV21 ||frame-pixel_format TOPSCODEC_PIX_FMT_P010 ||frame-pixel_format TOPSCODEC_PIX_FMT_P010LE) {int Y frame-linesize[0] * frame-height;int U frame-linesize[1] * ((frame-height 1) / 2);int V frame-linesize[2] * ((frame-height 1) / 2);}也就是说yuv数据的宽度是多大。 其实这个并不用手工来计算ffmpeg框架提供了专用的函数来处理 int av_image_fill_plane_sizes(size_t sizes[4], enum AVPixelFormat pix_fmt,int height, const ptrdiff_t linesizes[4])这个函数用来计算每个plane的长度是多少通过传入参数我们很容易看到height.原理和我们上面一样。 下面这个函数比较特殊可以计算linesizes也就是每个通道的stride. int av_image_fill_linesizes(int linesizes[4], enum AVPixelFormat pix_fmt, int width) 这个函数专门通过width和pix_fmt来计算linesizes[4]这样就不用我们通过手动来去计算了。 还有另外一个函数用来计算每个planes数据长度 该类函数族ffmpeg提供了很多具体在imgutils.h中 /*** Compute the size of an image line with format pix_fmt and width* width for the plane plane.** return the computed size in bytes/ int av_image_get_linesize(enum AVPixelFormat pix_fmt, int width, int plane);/** Fill plane linesizes for an image with pixel format pix_fmt and* width width.** param linesizes array to be filled with the linesize for each plane* return 0 in case of success, a negative error code otherwise/ int av_image_fill_linesizes(int linesizes[4], enum AVPixelFormat pix_fmt, int width);/** Fill plane sizes for an image with pixel format pix_fmt and height height.** param size the array to be filled with the size of each image plane* param linesizes the array containing the linesize for each* plane, should be filled by av_image_fill_linesizes()* return 0 in case of success, a negative error code otherwise** note The linesize parameters have the type ptrdiff_t here, while they are* int for av_image_fill_linesizes()./ int av_image_fill_plane_sizes(size_t size[4], enum AVPixelFormat pix_fmt,int height, const ptrdiff_t linesizes[4]);/** Fill plane data pointers for an image with pixel format pix_fmt and* height height.** param data pointers array to be filled with the pointer for each image plane* param ptr the pointer to a buffer which will contain the image* param linesizes the array containing the linesize for each* plane, should be filled by av_image_fill_linesizes()* return the size in bytes required for the image buffer, a negative* error code in case of failure*/ int av_image_fill_pointers(uint8_t *data[4], enum AVPixelFormat pix_fmt, int height,uint8_t ptr, const int linesizes[4]);/** Allocate an image with size w and h and pixel format pix_fmt, and* fill pointers and linesizes accordingly.* The allocated image buffer has to be freed by using* av_freep(pointers[0]).** param align the value to use for buffer size alignment* return the size in bytes required for the image buffer, a negative* error code in case of failure*/ int av_image_alloc(uint8_t pointers[4], int linesizes[4],int w, int h, enum AVPixelFormat pix_fmt, int align);/** Copy image plane from src to dst.* That is, copy height number of lines of bytewidth bytes each.* The first byte of each successive line is separated by _linesize bytes.** bytewidth must be contained by both absolute values of dst_linesize* and src_linesize, otherwise the function behavior is undefined.** param dst_linesize linesize for the image plane in dst* param src_linesize linesize for the image plane in src*/ void av_image_copy_plane(uint8_t *dst, int dst_linesize,const uint8_t src, int src_linesize,int bytewidth, int height);/** Copy image in src_data to dst_data.** param dst_linesizes linesizes for the image in dst_data* param src_linesizes linesizes for the image in src_data*/ void av_image_copy(uint8_t *dst_data[4], int dst_linesizes[4],const uint8_t src_data[4], const int src_linesizes[4],enum AVPixelFormat pix_fmt, int width, int height);/** Setup the data pointers and linesizes based on the specified image* parameters and the provided array.** The fields of the given image are filled in by using the src* address which points to the image data buffer. Depending on the* specified pixel format, one or multiple image data pointers and* line sizes will be set. If a planar format is specified, several* pointers will be set pointing to the different picture planes and* the line sizes of the different planes will be stored in the* lines_sizes array. Call with src NULL to get the required* size for the src buffer.** To allocate the buffer and fill in the dst_data and dst_linesize in* one call, use av_image_alloc().** param dst_data data pointers to be filled in* param dst_linesize linesizes for the image in dst_data to be filled in* param src buffer which will contain or contains the actual image data, can be NULL* param pix_fmt the pixel format of the image* param width the width of the image in pixels* param height the height of the image in pixels* param align the value used in src for linesize alignment* return the size in bytes required for src, a negative error code* in case of failure*/ int av_image_fill_arrays(uint8_t *dst_data[4], int dst_linesize[4],const uint8_t src,enum AVPixelFormat pix_fmt, int width, int height, int align);/** Return the size in bytes of the amount of data required to store an* image with the given parameters.** param pix_fmt the pixel format of the image* param width the width of the image in pixels* param height the height of the image in pixels* param align the assumed linesize alignment* return the buffer size in bytes, a negative error code in case of failure/ int av_image_get_buffer_size(enum AVPixelFormat pix_fmt, int width, int height, int align);/** Copy image data from an image into a buffer.** av_image_get_buffer_size() can be used to compute the required size* for the buffer to fill.** param dst a buffer into which picture data will be copied* param dst_size the size in bytes of dst* param src_data pointers containing the source image data* param src_linesize linesizes for the image in src_data* param pix_fmt the pixel format of the source image* param width the width of the source image in pixels* param height the height of the source image in pixels* param align the assumed linesize alignment for dst* return the number of bytes written to dst, or a negative value* (error code) on error*/ int av_image_copy_to_buffer(uint8_t *dst, int dst_size,const uint8_t * const src_data[4], const int src_linesize[4],enum AVPixelFormat pix_fmt, int width, int height, int align);/*** Check if the given dimension of an image is valid, meaning that all* bytes of the image can be addressed with a signed int.** param w the width of the picture* param h the height of the picture* param log_offset the offset to sum to the log level for logging with log_ctx* param log_ctx the parent logging context, it may be NULL* return 0 if valid, a negative error code otherwise*/ int av_image_check_size(unsigned int w, unsigned int h, int log_offset, void log_ctx);/** Check if the given dimension of an image is valid, meaning that all* bytes of a plane of an image with the specified pix_fmt can be addressed* with a signed int.** param w the width of the picture* param h the height of the picture* param max_pixels the maximum number of pixels the user wants to accept* param pix_fmt the pixel format, can be AV_PIX_FMT_NONE if unknown.* param log_offset the offset to sum to the log level for logging with log_ctx* param log_ctx the parent logging context, it may be NULL* return 0 if valid, a negative error code otherwise*/ int av_image_check_size2(unsigned int w, unsigned int h, int64_t max_pixels, enum AVPixelFormat pix_fmt, int log_offset, void *log_ctx); 2.成员函数 const char *av_get_colorspace_name(enum AVColorSpace val);AVFrame *av_frame_alloc(void);void av_frame_free(AVFrame frame);int av_frame_ref(AVFrame *dst, const AVFrame *src);AVFrame *av_frame_clone(const AVFrame *src);void av_frame_move_ref(AVFrame *dst, AVFrame *src);int av_frame_get_buffer(AVFrame *frame, int align);int av_frame_is_writable(AVFrame *frame);int av_frame_make_writable(AVFrame *frame);int av_frame_copy(AVFrame *dst, const AVFrame *src);int av_frame_copy_props(AVFrame *dst, const AVFrame *src);AVFrameSideData *av_frame_new_side_data(AVFrame *frame,enum AVFrameSideDataType type,size_t size);AVFrameSideData *av_frame_new_side_data_from_buf(AVFrame *frame,enum AVFrameSideDataType type,AVBufferRef *buf);void av_frame_remove_side_data(AVFrame *frame, enum AVFrameSideDataType type);const char *av_frame_side_data_name(enum AVFrameSideDataType type);上面函数核心就是操作AVFrame。 AVFrame Host内存的获取 av_frame_get_buffer ffmpeg提供了一个比较特殊的接口 /* Allocate new buffer(s) for audio or video data.** The following fields must be set on frame before calling this function:* - format (pixel format for video, sample format for audio)* - width and height for video* - nb_samples and channel_layout for audio** This function will fill AVFrame.data and AVFrame.buf arrays and, if* necessary, allocate and fill AVFrame.extended_data and AVFrame.extended_buf.* For planar formats, one buffer will be allocated for each plane.** warning: if frame already has been allocated, calling this function will* leak memory. In addition, undefined behavior can occur in certain* cases.** param frame frame in which to store the new buffers.* param align Required buffer size alignment. If equal to 0, alignment will be* chosen automatically for the current CPU. It is highly* recommended to pass 0 here unless you know what you are doing.** return 0 on success, a negative AVERROR on error.*/ int av_frame_get_buffer(AVFrame frame, int align)这个函数是用来从ffmpeg内存池中为frame中获取buf从上面的注释可以看到如果想要获取buf必须要设置 /** The following fields must be set on frame before calling this function: - format (pixel format for video, sample format for audio)* - width and height for video* - nb_samples and channel_layout for audio* /查看详细的函数代码 int av_frame_get_buffer(AVFrame frame, int align) {if (frame-format 0)return AVERROR(EINVAL);if (frame-width 0 frame-height 0)return get_video_buffer(frame, align);else if (frame-nb_samples 0 (frame-channel_layout || frame-channels 0))return get_audio_buffer(frame, align);return AVERROR(EINVAL); }详细的调用流程如下
AVFrame device内存获取av_hwframe_get_buffer 既然有host的内存获取那么就有device内存的获取 /** Allocate a new frame attached to the given AVHWFramesContext.** param hwframe_ctx a reference to an AVHWFramesContext* param frame an empty (freshly allocated or unreffed) frame to be filled with* newly allocated buffers.* param flags currently unused, should be set to zero* return 0 on success, a negative AVERROR code on failure*/ int av_hwframe_get_buffer(AVBufferRef *hwframe_ctx, AVFrame *frame, int flags);其调用流程如下注意分支代码这里是继承了父类后通过mmap去map到父类的内存上去。