OpenJPEG can decode in lower resolution or decode only a number
of enhancement layers.
---
libavcodec/libopenjpegdec.c | 28 ++++++++++++++++++++++++++++
1 files changed, 28 insertions(+), 0 deletions(-)
diff --git a/libavcodec/libopenjpegdec.c b/libavcodec/libopenjpegdec.c
index 799ccd7..53215a1 100644
--- a/libavcodec/libopenjpegdec.c
+++ b/libavcodec/libopenjpegdec.c
@@ -24,6 +24,7 @@
* JPEG 2000 decoder using libopenjpeg
*/
+#include "libavutil/opt.h"
#include "libavutil/imgutils.h"
#include "avcodec.h"
#include "libavutil/intreadwrite.h"
@@ -35,8 +36,11 @@
#define JP2_SIG_VALUE 0x0D0A870A
typedef struct {
+ AVClass *class;
opj_dparameters_t dec_params;
AVFrame image;
+ int lowres;
+ int lowqual;
} LibOpenJPEGContext;
static int check_image_attributes(opj_image_t *image)
@@ -104,6 +108,8 @@ static int libopenjpeg_decode_frame(AVCodecContext *avctx,
opj_set_event_mgr((opj_common_ptr)dec, NULL, NULL);
ctx->dec_params.cp_limit_decoding = LIMIT_TO_MAIN_HEADER;
+ ctx->dec_params.cp_reduce = ctx->lowres;
+ ctx->dec_params.cp_layer = ctx->lowqual;
// Tie decoder with decoding parameters
opj_setup_decoder(dec, &ctx->dec_params);
stream = opj_cio_open((opj_common_ptr)dec, buf, buf_size);
@@ -123,6 +129,12 @@ static int libopenjpeg_decode_frame(AVCodecContext *avctx,
}
width = image->x1 - image->x0;
height = image->y1 - image->y0;
+
+ if (ctx->lowres) {
+ width = (width + (1 << ctx->lowres) - 1) >> ctx->lowres;
+ height = (height + (1 << ctx->lowres) - 1) >> ctx->lowres;
+ }
+
if(av_image_check_size(width, height, 0, avctx) < 0) {
av_log(avctx, AV_LOG_ERROR, "%dx%d dimension invalid.\n", width,
height);
goto done;
@@ -208,6 +220,21 @@ static av_cold int libopenjpeg_decode_close(AVCodecContext
*avctx)
return 0 ;
}
+#define OFFSET(x) offsetof(LibOpenJPEGContext, x)
+#define VD AV_OPT_FLAG_VIDEO_PARAM | AV_OPT_FLAG_DECODING_PARAM
+
+static const AVOption options[] = {
+ { "lowqual", "Low quality decoding", OFFSET(lowqual),
AV_OPT_TYPE_INT, { 0 }, 0, INT_MAX, VD },
+ { "lowres", "Low resolution decoding", OFFSET(lowres),
AV_OPT_TYPE_INT, { 0 }, 0, INT_MAX, VD },
+ { NULL },
+};
+
+static const AVClass class = {
+ .class_name = "libopenjpeg",
+ .item_name = av_default_item_name,
+ .option = options,
+ .version = LIBAVUTIL_VERSION_INT,
+};
AVCodec ff_libopenjpeg_decoder = {
.name = "libopenjpeg",
@@ -219,5 +246,6 @@ AVCodec ff_libopenjpeg_decoder = {
.decode = libopenjpeg_decode_frame,
.capabilities = CODEC_CAP_DR1 | CODEC_CAP_FRAME_THREADS,
.long_name = NULL_IF_CONFIG_SMALL("OpenJPEG based JPEG 2000
decoder"),
+ .priv_class = &class,
.init_thread_copy =
ONLY_IF_THREADS_ENABLED(libopenjpeg_decode_init_thread_copy),
};
--
1.7.8.rc1
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