ffmpeg之AVFrame

结构体说明

原始数据的相关信息结构体

/**
 * This structure describes decoded (raw) audio or video data.
 * 此结构描述解码后的(未编码前的)原始音频或者视频数据
 * AVFrame must be allocated using av_frame_alloc(). Note that this only
 * allocates the AVFrame itself, the buffers for the data must be managed
 * through other means (see below).
 * AVFrame must be freed with av_frame_free().
 * AVFrame必须使用av_frame_alloc进行分配,重点是只会分配AVFrame本身,不会分配存储真实数据的buffer
 * AVFrame必须使用av_frame_free进行释放。
 * AVFrame is typically allocated once and then reused multiple times to hold
 * different data (e.g. a single AVFrame to hold frames received from a
 * decoder). In such a case, av_frame_unref() will free any references held by
 * the frame and reset it to its original clean state before it
 * is reused again.
 * AVFrame通常一次分配,多次使用(while前alloc,后free,内部多次使用,av_frame_unref会释放buffe的所有引用,并将其置为原始干净状态,然后再次使用)
 * The data described by an AVFrame is usually reference counted through the
 * AVBuffer API. The underlying buffer references are stored in AVFrame.buf /
 * AVFrame.extended_buf. An AVFrame is considered to be reference counted if at
 * least one reference is set, i.e. if AVFrame.buf[0] != NULL. In such a case,
 * every single data plane must be contained in one of the buffers in
 * AVFrame.buf or AVFrame.extended_buf.
 * There may be a single buffer for all the data, or one separate buffer for
 * each plane, or anything in between.
 * AVFrame的原始数据有引用计数进行内存管理;
 * 对于planar存储的数据格式,多通道数据存储在二维数组data中
 * sizeof(AVFrame) is not a part of the public ABI, so new fields may be added
 * to the end with a minor bump.
 *
 * Fields can be accessed through AVOptions, the name string used, matches the
 * C structure field name for fields accessible through AVOptions. The AVClass
 * for AVFrame can be obtained from avcodec_get_frame_class()
 */
typedef struct AVFrame {
#define AV_NUM_DATA_POINTERS 8
    /**
     * pointer to the picture/channel planes.
     * This might be different from the first allocated byte
     *
     * 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: Except for hwaccel formats, pointers not needed by the format
     * MUST be set to NULL.
     * 编码前的原始图片或者声音数据,最多存储8个通道的数据
     */
    uint8_t *data[AV_NUM_DATA_POINTERS];

    /**
     * For video, size in bytes of each picture line.
     * For audio, size in bytes of each plane.
     * 对于视频,每张图片行的大小(以字节为单位)
     * 对应音频,每个通道的大小(以字节为单位)
     * For audio, only linesize[0] may be set. For planar audio, each channel
     * plane must be the same size.
     * 对于音频,智能设置linesize[0],对于planar,每个通道必须相同的linesize
     * 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.
     * 对于视频,16或者32的倍数
     * @note The linesize may be larger than the size of usable data -- there
     * may be extra padding present for performance reasons.
     * 出于性能原因,可能存在额外的填充
     */
    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.
     * 对于需求更多通道的音频,必须使用extended_data
     */
    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".
     * @{
     * 视频参数
     */
    int width, height;
    /**
     * @}
     */

    /**
     * number of audio samples (per channel) described by this frame
     * 音频参数
     */
    int nb_samples;

    /**
     * format of the frame, -1 if unknown or unset
     * Values correspond to enum AVPixelFormat for video frames,
     * enum AVSampleFormat for audio)
     * 未知或者未设置则为-1
     * 音频的AVSampleForamt,视频的AVPixelFormat
     */
    int format;

    /**
     * 1 -> keyframe, 0-> not
     * 关键帧
     */
    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;

#if FF_API_PKT_PTS
    /**
     * PTS copied from the AVPacket that was decoded to produce this frame.
     * @deprecated use the pts field instead
     */
    attribute_deprecated
    int64_t pkt_pts;      // 不再使用
#endif

    /**
     * DTS copied from the AVPacket that triggered returning this frame. (if frame threading isn't used)
     * This is also the Presentation time of this AVFrame calculated from
     * only AVPacket.dts values without pts values.
     */
    int64_t pkt_dts;

    /**
     * picture number in bitstream order
     * 解码后index, 0I 3B 2B 4B 5P
     */
    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;

#if FF_API_ERROR_FRAME
    /**
     * @deprecated unused
     */
    attribute_deprecated
    uint64_t error[AV_NUM_DATA_POINTERS];
#endif

    /**
     * When decoding, this signals how much the picture must be delayed.
     * extra_delay = repeat_pict / (2*fps)
     */
    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.
     * 音频采样率
     */
    int sample_rate;

    /**
     * Channel layout of the audio data.
     * 量化格式
     */
    uint64_t channel_layout;

    /**
     * AVBuffer references backing the data for this frame. If all elements of
     * this array are NULL, then this frame is not reference counted. 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.
     * 同data
     */
    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().
     * 同extended_data
     */
    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 shouldn't 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.
     * 通道数
     */
    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.
     * 此Frame的数据长度
     */
    int pkt_size;

#if FF_API_FRAME_QP
    /**
     * QP table
     */
    attribute_deprecated
    int8_t *qscale_table;
    /**
     * QP store stride
     */
    attribute_deprecated
    int qstride;

    attribute_deprecated
    int qscale_type;

    attribute_deprecated
    AVBufferRef *qp_table_buf;
#endif
    /**
     * 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 frame's 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 frame's private_ref field.
     */
    AVBufferRef *private_ref;
} AVFrame;

/**
 * @}
 * @}
 * @defgroup lavu_picture Image related
 *
 * AVPicture types, pixel formats and basic image planes manipulation.
 *
 * @{
 */

enum AVPictureType {
    AV_PICTURE_TYPE_NONE = 0, ///< Undefined
    AV_PICTURE_TYPE_I,     ///< Intra
    AV_PICTURE_TYPE_P,     ///< Predicted
    AV_PICTURE_TYPE_B,     ///< Bi-dir predicted
    AV_PICTURE_TYPE_S,     ///< S(GMC)-VOP MPEG-4
    AV_PICTURE_TYPE_SI,    ///< Switching Intra
    AV_PICTURE_TYPE_SP,    ///< Switching Predicted
    AV_PICTURE_TYPE_BI,    ///< BI type
};

相关函数

av_frame_alloc

/**
 * Allocate an AVFrame and set its fields to default values.  The resulting
 * struct must be freed using av_frame_free().
 *
 * @return An AVFrame filled with default values or NULL on failure.
 *
 * @note this only allocates the AVFrame itself, not the data buffers. Those
 * must be allocated through other means, e.g. with av_frame_get_buffer() or
 * manually.
 */
AVFrame *av_frame_alloc(void)
{
    AVFrame *frame = av_mallocz(sizeof(*frame));

    if (!frame)
        return NULL;

    frame->extended_data = NULL;
    get_frame_defaults(frame);

    return frame;
}

av_frame_free

/**
 * Free the frame and any dynamically allocated objects in it,
 * e.g. extended_data. If the frame is reference counted, it will be
 * unreferenced first.
 *
 * @param frame frame to be freed. The pointer will be set to NULL.
 */
void av_frame_free(AVFrame **frame)
{
    if (!frame || !*frame)
        return;

    av_frame_unref(*frame);
    av_freep(frame);
}

av_framme_ref

/**
 * Set up a new reference to the data described by the source frame.
 *
 * Copy frame properties from src to dst and create a new reference for each
 * AVBufferRef from src.
 *
 * If src is not reference counted, new buffers are allocated and the data is
 * copied.
 *
 * @warning: dst MUST have been either unreferenced with av_frame_unref(dst),
 *           or newly allocated with av_frame_alloc() before calling this
 *           function, or undefined behavior will occur.
 *
 * @return 0 on success, a negative AVERROR on error
 */
int av_frame_ref(AVFrame *dst, const AVFrame *src)
{
    int i, ret = 0;

    av_assert1(dst->width == 0 && dst->height == 0);
    av_assert1(dst->channels == 0);

    dst->format         = src->format;
    dst->width          = src->width;
    dst->height         = src->height;
    dst->channels       = src->channels;
    dst->channel_layout = src->channel_layout;
    dst->nb_samples     = src->nb_samples;

    ret = frame_copy_props(dst, src, 0);
    if (ret < 0)
        return ret;

    /* duplicate the frame data if it's not refcounted */
    if (!src->buf[0]) {
        ret = av_frame_get_buffer(dst, 32);
        if (ret < 0)
            return ret;

        ret = av_frame_copy(dst, src);
        if (ret < 0)
            av_frame_unref(dst);

        return ret;
    }

    /* ref the buffers */
    for (i = 0; i < FF_ARRAY_ELEMS(src->buf); i++) {
        if (!src->buf[i])
            continue;
        dst->buf[i] = av_buffer_ref(src->buf[i]);
        if (!dst->buf[i]) {
            ret = AVERROR(ENOMEM);
            goto fail;
        }
    }

    if (src->extended_buf) {
        dst->extended_buf = av_mallocz_array(sizeof(*dst->extended_buf),
                                       src->nb_extended_buf);
        if (!dst->extended_buf) {
            ret = AVERROR(ENOMEM);
            goto fail;
        }
        dst->nb_extended_buf = src->nb_extended_buf;

        for (i = 0; i < src->nb_extended_buf; i++) {
            dst->extended_buf[i] = av_buffer_ref(src->extended_buf[i]);
            if (!dst->extended_buf[i]) {
                ret = AVERROR(ENOMEM);
                goto fail;
            }
        }
    }

    if (src->hw_frames_ctx) {
        dst->hw_frames_ctx = av_buffer_ref(src->hw_frames_ctx);
        if (!dst->hw_frames_ctx) {
            ret = AVERROR(ENOMEM);
            goto fail;
        }
    }

    /* duplicate extended data */
    if (src->extended_data != src->data) {
        int ch = src->channels;

        if (!ch) {
            ret = AVERROR(EINVAL);
            goto fail;
        }
        CHECK_CHANNELS_CONSISTENCY(src);

        dst->extended_data = av_malloc_array(sizeof(*dst->extended_data), ch);
        if (!dst->extended_data) {
            ret = AVERROR(ENOMEM);
            goto fail;
        }
        memcpy(dst->extended_data, src->extended_data, sizeof(*src->extended_data) * ch);
    } else
        dst->extended_data = dst->data;

    memcpy(dst->data,     src->data,     sizeof(src->data));
    memcpy(dst->linesize, src->linesize, sizeof(src->linesize));

    return 0;

fail:
    av_frame_unref(dst);
    return ret;
}

av_frame_unref

/**
 * Unreference all the buffers referenced by frame and reset the frame fields.
 */
void av_frame_unref(AVFrame *frame)
{
    int i;

    if (!frame)
        return;

    wipe_side_data(frame);

    for (i = 0; i < FF_ARRAY_ELEMS(frame->buf); i++)
        av_buffer_unref(&frame->buf[i]);
    for (i = 0; i < frame->nb_extended_buf; i++)
        av_buffer_unref(&frame->extended_buf[i]);
    av_freep(&frame->extended_buf);
    av_dict_free(&frame->metadata);
#if FF_API_FRAME_QP
FF_DISABLE_DEPRECATION_WARNINGS
    av_buffer_unref(&frame->qp_table_buf);
FF_ENABLE_DEPRECATION_WARNINGS
#endif

    av_buffer_unref(&frame->hw_frames_ctx);

    av_buffer_unref(&frame->opaque_ref);
    av_buffer_unref(&frame->private_ref);

    get_frame_defaults(frame);
}

static void get_frame_defaults(AVFrame *frame)
{
    if (frame->extended_data != frame->data)
        av_freep(&frame->extended_data);

    memset(frame, 0, sizeof(*frame));

    frame->pts                   =
    frame->pkt_dts               = AV_NOPTS_VALUE;
#if FF_API_PKT_PTS
FF_DISABLE_DEPRECATION_WARNINGS
    frame->pkt_pts               = AV_NOPTS_VALUE;
FF_ENABLE_DEPRECATION_WARNINGS
#endif
    frame->best_effort_timestamp = AV_NOPTS_VALUE;
    frame->pkt_duration        = 0;
    frame->pkt_pos             = -1;
    frame->pkt_size            = -1;
    frame->key_frame           = 1;
    frame->sample_aspect_ratio = (AVRational){ 0, 1 };
    frame->format              = -1; /* unknown */
    frame->extended_data       = frame->data;
    frame->color_primaries     = AVCOL_PRI_UNSPECIFIED;
    frame->color_trc           = AVCOL_TRC_UNSPECIFIED;
    frame->colorspace          = AVCOL_SPC_UNSPECIFIED;
    frame->color_range         = AVCOL_RANGE_UNSPECIFIED;
    frame->chroma_location     = AVCHROMA_LOC_UNSPECIFIED;
    frame->flags               = 0;
}

av_frame_move_ref

/**
 * Move everything contained in src to dst and reset src.
 *
 * @warning: dst is not unreferenced, but directly overwritten without reading
 *           or deallocating its contents. Call av_frame_unref(dst) manually
 *           before calling this function to ensure that no memory is leaked.
 */
void av_frame_move_ref(AVFrame *dst, AVFrame *src)
{
    av_assert1(dst->width == 0 && dst->height == 0);
    av_assert1(dst->channels == 0);

    *dst = *src;
    if (src->extended_data == src->data)
        dst->extended_data = dst->data;
    memset(src, 0, sizeof(*src));
    get_frame_defaults(src);
}

av_frame_clone

/**
 * Create a new frame that references the same data as src.
 *
 * This is a shortcut for av_frame_alloc()+av_frame_ref().
 *
 * @return newly created AVFrame on success, NULL on error.
 */
AVFrame *av_frame_clone(const AVFrame *src)
{
    AVFrame *ret = av_frame_alloc();

    if (!ret)
        return NULL;

    if (av_frame_ref(ret, src) < 0)
        av_frame_free(&ret);

    return ret;
}

av_frame_is_writable

/**
 * Check if the frame data is writable.
 *
 * @return A positive value if the frame data is writable (which is true if and
 * only if each of the underlying buffers has only one reference, namely the one
 * stored in this frame). Return 0 otherwise.
 *
 * If 1 is returned the answer is valid until av_buffer_ref() is called on any
 * of the underlying AVBufferRefs (e.g. through av_frame_ref() or directly).
 *
 * @see av_frame_make_writable(), av_buffer_is_writable()
 */
int av_frame_is_writable(AVFrame *frame)
{
    int i, ret = 1;

    /* assume non-refcounted frames are not writable */
    if (!frame->buf[0])
        return 0;

    for (i = 0; i < FF_ARRAY_ELEMS(frame->buf); i++)
        if (frame->buf[i])
            ret &= !!av_buffer_is_writable(frame->buf[i]);
    for (i = 0; i < frame->nb_extended_buf; i++)
        ret &= !!av_buffer_is_writable(frame->extended_buf[i]);

    return ret;
}

av_frame_make_writable

/**
 * Ensure that the frame data is writable, avoiding data copy if possible.
 *
 * Do nothing if the frame is writable, allocate new buffers and copy the data
 * if it is not.
 *
 * @return 0 on success, a negative AVERROR on error.
 *
 * @see av_frame_is_writable(), av_buffer_is_writable(),
 * av_buffer_make_writable()
 */
int av_frame_make_writable(AVFrame *frame)
{
    AVFrame tmp;
    int ret;

    if (!frame->buf[0])
        return AVERROR(EINVAL);

    if (av_frame_is_writable(frame))
        return 0;

    memset(&tmp, 0, sizeof(tmp));
    tmp.format         = frame->format;
    tmp.width          = frame->width;
    tmp.height         = frame->height;
    tmp.channels       = frame->channels;
    tmp.channel_layout = frame->channel_layout;
    tmp.nb_samples     = frame->nb_samples;
    ret = av_frame_get_buffer(&tmp, 32);
    if (ret < 0)
        return ret;

    ret = av_frame_copy(&tmp, frame);
    if (ret < 0) {
        av_frame_unref(&tmp);
        return ret;
    }

    ret = av_frame_copy_props(&tmp, frame);
    if (ret < 0) {
        av_frame_unref(&tmp);
        return ret;
    }

    av_frame_unref(frame);

    *frame = tmp;
    if (tmp.data == tmp.extended_data)
        frame->extended_data = frame->data;

    return 0;
}

av_frame_get_buffer

/**
 * 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)
{
    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);
}

static int get_video_buffer(AVFrame *frame, int align)
{
    const AVPixFmtDescriptor *desc = av_pix_fmt_desc_get(frame->format);
    int ret, i, padded_height;
    int plane_padding = FFMAX(16 + 16/*STRIDE_ALIGN*/, align);

    if (!desc)
        return AVERROR(EINVAL);

    if ((ret = av_image_check_size(frame->width, frame->height, 0, NULL)) < 0)
        return ret;

    if (!frame->linesize[0]) {
        if (align <= 0)
            align = 32; /* STRIDE_ALIGN. Should be av_cpu_max_align() */

        for(i=1; i<=align; i+=i) {
            ret = av_image_fill_linesizes(frame->linesize, frame->format,
                                          FFALIGN(frame->width, i));
            if (ret < 0)
                return ret;
            if (!(frame->linesize[0] & (align-1)))
                break;
        }

        for (i = 0; i < 4 && frame->linesize[i]; i++)
            frame->linesize[i] = FFALIGN(frame->linesize[i], align);
    }

    padded_height = FFALIGN(frame->height, 32);
    if ((ret = av_image_fill_pointers(frame->data, frame->format, padded_height,
                                      NULL, frame->linesize)) < 0)
        return ret;

    frame->buf[0] = av_buffer_alloc(ret + 4*plane_padding);
    if (!frame->buf[0]) {
        ret = AVERROR(ENOMEM);
        goto fail;
    }

    if ((ret = av_image_fill_pointers(frame->data, frame->format, padded_height,
                                      frame->buf[0]->data, frame->linesize)) < 0)
        goto fail;

    for (i = 1; i < 4; i++) {
        if (frame->data[i])
            frame->data[i] += i * plane_padding;
    }

    frame->extended_data = frame->data;

    return 0;
fail:
    av_frame_unref(frame);
    return ret;
}

static int get_audio_buffer(AVFrame *frame, int align)
{
    int channels;
    int planar   = av_sample_fmt_is_planar(frame->format);
    int planes;
    int ret, i;

    if (!frame->channels)
        frame->channels = av_get_channel_layout_nb_channels(frame->channel_layout);

    channels = frame->channels;
    planes = planar ? channels : 1;

    CHECK_CHANNELS_CONSISTENCY(frame);
    if (!frame->linesize[0]) {
        ret = av_samples_get_buffer_size(&frame->linesize[0], channels,
                                         frame->nb_samples, frame->format,
                                         align);
        if (ret < 0)
            return ret;
    }

    if (planes > AV_NUM_DATA_POINTERS) {
        frame->extended_data = av_mallocz_array(planes,
                                          sizeof(*frame->extended_data));
        frame->extended_buf  = av_mallocz_array((planes - AV_NUM_DATA_POINTERS),
                                          sizeof(*frame->extended_buf));
        if (!frame->extended_data || !frame->extended_buf) {
            av_freep(&frame->extended_data);
            av_freep(&frame->extended_buf);
            return AVERROR(ENOMEM);
        }
        frame->nb_extended_buf = planes - AV_NUM_DATA_POINTERS;
    } else
        frame->extended_data = frame->data;

    for (i = 0; i < FFMIN(planes, AV_NUM_DATA_POINTERS); i++) {
        frame->buf[i] = av_buffer_alloc(frame->linesize[0]);
        if (!frame->buf[i]) {
            av_frame_unref(frame);
            return AVERROR(ENOMEM);
        }
        frame->extended_data[i] = frame->data[i] = frame->buf[i]->data;
    }
    for (i = 0; i < planes - AV_NUM_DATA_POINTERS; i++) {
        frame->extended_buf[i] = av_buffer_alloc(frame->linesize[0]);
        if (!frame->extended_buf[i]) {
            av_frame_unref(frame);
            return AVERROR(ENOMEM);
        }
        frame->extended_data[i + AV_NUM_DATA_POINTERS] = frame->extended_buf[i]->data;
    }
    return 0;

}

av_frame_get_planar_buffer

/**
 * Get the buffer reference a given data plane is stored in.
 *
 * @param plane index of the data plane of interest in frame->extended_data.
 *
 * @return the buffer reference that contains the plane or NULL if the input
 * frame is not valid.
 */
AVBufferRef *av_frame_get_plane_buffer(AVFrame *frame, int plane)
{
    uint8_t *data;
    int planes, i;

    if (frame->nb_samples) {
        int channels = frame->channels;
        if (!channels)
            return NULL;
        CHECK_CHANNELS_CONSISTENCY(frame);
        planes = av_sample_fmt_is_planar(frame->format) ? channels : 1;
    } else
        planes = 4;

    if (plane < 0 || plane >= planes || !frame->extended_data[plane])
        return NULL;
    data = frame->extended_data[plane];

    for (i = 0; i < FF_ARRAY_ELEMS(frame->buf) && frame->buf[i]; i++) {
        AVBufferRef *buf = frame->buf[i];
        if (data >= buf->data && data < buf->data + buf->size)
            return buf;
    }
    for (i = 0; i < frame->nb_extended_buf; i++) {
        AVBufferRef *buf = frame->extended_buf[i];
        if (data >= buf->data && data < buf->data + buf->size)
            return buf;
    }
    return NULL;
}

frame_copy_video

static int frame_copy_video(AVFrame *dst, const AVFrame *src)
{
    const uint8_t *src_data[4];
    int i, planes;

    if (dst->width  < src->width ||
        dst->height < src->height)
        return AVERROR(EINVAL);

    planes = av_pix_fmt_count_planes(dst->format);
    for (i = 0; i < planes; i++)
        if (!dst->data[i] || !src->data[i])
            return AVERROR(EINVAL);

    memcpy(src_data, src->data, sizeof(src_data));
    av_image_copy(dst->data, dst->linesize,
                  src_data, src->linesize,
                  dst->format, src->width, src->height);

    return 0;
}

frame_copy_audio

static int frame_copy_audio(AVFrame *dst, const AVFrame *src)
{
    int planar   = av_sample_fmt_is_planar(dst->format);
    int channels = dst->channels;
    int planes   = planar ? channels : 1;
    int i;

    if (dst->nb_samples     != src->nb_samples ||
        dst->channels       != src->channels ||
        dst->channel_layout != src->channel_layout)
        return AVERROR(EINVAL);

    CHECK_CHANNELS_CONSISTENCY(src);

    for (i = 0; i < planes; i++)
        if (!dst->extended_data[i] || !src->extended_data[i])
            return AVERROR(EINVAL);

    av_samples_copy(dst->extended_data, src->extended_data, 0, 0,
                    dst->nb_samples, channels, dst->format);

    return 0;
}

本文来自博客园,作者:faithlocus,转载请注明原文链接:https://www.cnblogs.com/faithlocus/p/15636173.html

原文地址:https://www.cnblogs.com/faithlocus/p/15636173.html