On Tue, Dec 27, 2016 at 7:31 PM, Anton Khirnov <[email protected]> wrote:
> Also, add generic code for handling cropping, so the decoders can export
> just the cropping size and not bother with the rest.
> ---
> doc/APIchanges | 4 ++
> libavcodec/avcodec.h | 22 +++++++++
> libavcodec/decode.c | 112
> ++++++++++++++++++++++++++++++++++++++++++++-
> libavcodec/internal.h | 6 +++
> libavcodec/options_table.h | 1 +
> libavcodec/version.h | 4 +-
> 6 files changed, 146 insertions(+), 3 deletions(-)
>
> diff --git a/doc/APIchanges b/doc/APIchanges
> index 10a2da4..a0ef198 100644
> --- a/doc/APIchanges
> +++ b/doc/APIchanges
> @@ -13,6 +13,10 @@ libavutil: 2015-08-28
>
> API changes, most recent first:
>
> +2016-xx-xx - xxxxxxx - lavc 57.31.0 - avcodec.h
> + Add AVCodecContext.apply_cropping to control whether cropping
> + is handled by libavcodec or the caller.
> +
> 2016-xx-xx - xxxxxxx - lavu 55.30.0 - frame.h
> Add AVFrame.crop_left/right/top/bottom fields for attaching cropping
> information to video frames.
> diff --git a/libavcodec/avcodec.h b/libavcodec/avcodec.h
> index 95da50b..524e06a 100644
> --- a/libavcodec/avcodec.h
> +++ b/libavcodec/avcodec.h
> @@ -3112,6 +3112,28 @@ typedef struct AVCodecContext {
> * This field should be set before avcodec_open2() is called.
> */
> AVBufferRef *hw_frames_ctx;
> +
> + /**
> + * Video decoding only. Certain video codecs support cropping, meaning
> that
> + * only a sub-rectangle of the decoded frame is intended for display.
> This
> + * option controls how cropping is handled by libavcodec.
> + *
> + * When set to 1 (the default), libavcodec will apply cropping
> internally.
> + * I.e. it will modify the output frame width/height fields and offset
> the
> + * data pointers (only by as much as possible while preserving
> alignment, or
> + * by the full amount if the AV_CODEC_FLAG_UNALIGNED flag is set) so that
> + * the frames output by the decoder refer only to the cropped area. The
> + * crop_* fields of the output frames will be zero.
> + *
> + * When set to 0, the width/height fields of the output frames will be
> set
> + * to the coded dimensions and the crop_* fields will describe the
> cropping
> + * rectangle. Applying the cropping is left to the caller.
> + *
> + * When hardware acceleration with opaque output frames is used, the
> actual
> + * value of this option is disregarded and libavcodec behaves as if it
> was
> + * set to 0.
> + */
> + int apply_cropping;
Why is this a new field? As long as it is used to convey a boolean
state isn't a codec flag more efficient?
> } AVCodecContext;
>
> /**
> diff --git a/libavcodec/decode.c b/libavcodec/decode.c
> index 0fd41ab..65ee8b0 100644
> --- a/libavcodec/decode.c
> +++ b/libavcodec/decode.c
> @@ -29,6 +29,7 @@
> #include "libavutil/frame.h"
> #include "libavutil/hwcontext.h"
> #include "libavutil/imgutils.h"
> +#include "libavutil/intmath.h"
>
> #include "avcodec.h"
> #include "bytestream.h"
> @@ -450,6 +451,106 @@ int attribute_align_arg
> avcodec_send_packet(AVCodecContext *avctx, const AVPacke
> return 0;
> }
>
> +static int calc_cropping_offsets(size_t offsets[4], const AVFrame *frame,
> + const AVPixFmtDescriptor *desc)
IMO passing desc here is not ideal, deriving it from frame seems more
usual to me
> +{
> + int i, j;
> +
> + for (i = 0; frame->data[i]; i++) {
> + const AVComponentDescriptor *comp = NULL;
> + int shift_x = (i == 1 || i == 2) ? desc->log2_chroma_w : 0;
> + int shift_y = (i == 1 || i == 2) ? desc->log2_chroma_h : 0;
> +
> + if (desc->flags & (AV_PIX_FMT_FLAG_PAL | AV_PIX_FMT_FLAG_PSEUDOPAL)
> && i == 1) {
> + offsets[i] = 0;
> + break;
> + }
> +
> + /* find any component descriptor for this plane */
> + for (j = 0; j < desc->nb_components; j++) {
> + if (desc->comp[j].plane == i) {
> + comp = &desc->comp[j];
> + break;
> + }
> + }
> + if (!comp)
> + return AVERROR_BUG;
> +
> + offsets[i] = (frame->crop_top >> shift_y) * frame->linesize[i] +
> + (frame->crop_left >> shift_x) * comp->step;
> + }
> +
> + return 0;
> +}
> +
> +static int apply_cropping(AVCodecContext *avctx, AVFrame *frame)
> +{
> + const AVPixFmtDescriptor *desc;
> + size_t offsets[4];
> + int i;
> +
> + /* make sure we are noisy about decoders returning invalid cropping data
> */
> + if (frame->crop_left >= INT_MAX - frame->crop_right ||
> + frame->crop_top >= INT_MAX - frame->crop_bottom ||
> + (frame->crop_left + frame->crop_right) >= frame->width ||
> + (frame->crop_top + frame->crop_bottom) >= frame->height) {
> + av_log(avctx, AV_LOG_WARNING,
> + "Invalid cropping information set by a decoder:
> %zu/%zu/%zu/%zu "
> + "(frame size %dx%d). This is a bug, please report it\n",
> + frame->crop_left, frame->crop_right, frame->crop_top,
> frame->crop_bottom,
> + frame->width, frame->height);
> + frame->crop_left = 0;
> + frame->crop_right = 0;
> + frame->crop_top = 0;
> + frame->crop_bottom = 0;
> + return 0;
> + }
> +
> + if (!avctx->apply_cropping)
> + return 0;
> +
> + desc = av_pix_fmt_desc_get(frame->format);
> + if (!desc)
> + return AVERROR_BUG;
> +
> + /* Do nothing for hwaccel formats.
> + * Bitstream formats cannot be easily handled here either (and
> corresponding
> + * decoders should not export any cropping anyway), so also do nothing
> for
> + * those. */
> + if (desc->flags & (AV_PIX_FMT_FLAG_BITSTREAM | AV_PIX_FMT_FLAG_HWACCEL))
> + return 0;
> +
> + /* calculate the offsets for each plane */
> + calc_cropping_offsets(offsets, frame, desc);
unchecked return value
--
Vittorio
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