Up until now, the JPEG-LS encoder allocated a worst-case-sized packet
at the beginning of each encode2 call; then it wrote the packet header
into its destination buffer and encoded the actual packet data;
said data is written into another worst-case-sized buffer, because it
needs to be escaped before being written into the packet buffer.
Finally, because the packet buffer is worst-case-sized, the generic
code copies the actually used part into a fresh buffer.
This commit changes this: Allocating the packet and writing the header
into it is deferred until the actual data has been encoded and its size
is known. This gives a good upper bound for the needed size of the packet
buffer (the upper bound might be 1/15 too large) and so one can avoid the
implicit intermediate buffer and support user-supplied buffers by using
ff_get_encode_buffer().
Signed-off-by: Andreas Rheinhardt <andreas.rheinha...@outlook.com>
---
libavcodec/jpeglsenc.c | 102 ++++++++++++++++++++++++-----------------
1 file changed, 59 insertions(+), 43 deletions(-)
diff --git a/libavcodec/jpeglsenc.c b/libavcodec/jpeglsenc.c
index 17d46c0449..a7bcd78275 100644
--- a/libavcodec/jpeglsenc.c
+++ b/libavcodec/jpeglsenc.c
@@ -27,6 +27,7 @@
#include "avcodec.h"
#include "bytestream.h"
+#include "encode.h"
#include "get_bits.h"
#include "put_bits.h"
#include "golomb.h"
@@ -283,53 +284,23 @@ static int encode_picture_ls(AVCodecContext *avctx,
AVPacket *pkt,
const uint8_t *in;
uint8_t *last = NULL;
JLSState state = { 0 };
- int i, size, ret;
+ size_t size;
+ int i, ret, size_in_bits;
int comps;
- if ((ret = ff_alloc_packet2(avctx, pkt, ctx->size, 0)) < 0)
- return ret;
-
last = av_mallocz(FFABS(p->linesize[0]));
if (!last)
return AVERROR(ENOMEM);
- bytestream2_init_writer(&pb, pkt->data, pkt->size);
init_put_bits(&pb2, ctx->buf, ctx->size);
- /* write our own JPEG header, can't use mjpeg_picture_header */
comps = ctx->comps;
- put_marker_byteu(&pb, SOI);
- put_marker_byteu(&pb, SOF48);
- bytestream2_put_be16u(&pb, 8 + comps * 3); // header size depends on
components
- bytestream2_put_byteu(&pb, (avctx->pix_fmt == AV_PIX_FMT_GRAY16) ? 16 :
8); // bpp
- bytestream2_put_be16u(&pb, avctx->height);
- bytestream2_put_be16u(&pb, avctx->width);
- bytestream2_put_byteu(&pb, comps); // components
- for (i = 1; i <= comps; i++) {
- bytestream2_put_byteu(&pb, i); // component ID
- bytestream2_put_byteu(&pb, 0x11); // subsampling: none
- bytestream2_put_byteu(&pb, 0); // Tiq, used by JPEG-LS ext
- }
-
- put_marker_byteu(&pb, SOS);
- bytestream2_put_be16u(&pb, 6 + comps * 2);
- bytestream2_put_byteu(&pb, comps);
- for (i = 1; i <= comps; i++) {
- bytestream2_put_byteu(&pb, i); // component ID
- bytestream2_put_byteu(&pb, 0); // mapping index: none
- }
- bytestream2_put_byteu(&pb, ctx->pred);
- bytestream2_put_byteu(&pb, (comps > 1) ? 1 : 0); // interleaving: 0 -
plane, 1 - line
- bytestream2_put_byteu(&pb, 0); // point transform: none
-
/* initialize JPEG-LS state from JPEG parameters */
state.near = ctx->pred;
state.bpp = (avctx->pix_fmt == AV_PIX_FMT_GRAY16) ? 16 : 8;
ff_jpegls_reset_coding_parameters(&state, 0);
ff_jpegls_init_state(&state);
- ls_store_lse(&state, &pb);
-
in = p->data[0];
if (avctx->pix_fmt == AV_PIX_FMT_GRAY8) {
int t = 0;
@@ -378,17 +349,63 @@ static int encode_picture_ls(AVCodecContext *avctx,
AVPacket *pkt,
in += p->linesize[0];
}
}
-
- /* the specification says that after doing 0xff escaping unused bits in
- * the last byte must be set to 0, so just append 7 "optional" zero bits
- * to avoid special-casing. */
+ av_free(last);
+ /* Now the actual image data has been written, which enables us to estimate
+ * the needed packet size: For every 15 input bits, an escape bit might be
+ * added below; and if put_bits_count % 15 is >= 8, then another bit might
+ * be added.
+ * Furthermore the specification says that after doing 0xff escaping unused
+ * bits in the last byte must be set to 0, so just append 7 "optional" zero
+ * bits to avoid special-casing. This also simplifies the size calculation:
+ * Properly rounding up is now automatically baked-in. */
put_bits(&pb2, 7, 0);
- size = put_bits_count(&pb2);
+ /* Make sure that the bit count + padding is representable in an int;
+ necessary for put_bits_count() as well as for using a GetBitContext. */
+ if (put_bytes_count(&pb2, 0) > INT_MAX / 8 - AV_INPUT_BUFFER_PADDING_SIZE)
+ return AVERROR(ERANGE);
+ size_in_bits = put_bits_count(&pb2);
flush_put_bits(&pb2);
+ size = size_in_bits * 2U / 15;
+ size += 2 + 2 + 2 + 1 + 2 + 2 + 1 + comps * (1 + 1 + 1) + 2 + 2 + 1
+ + comps * (1 + 1) + 1 + 1 + 1; /* Header */
+ size += 2 + 2 + 1 + 2 + 2 + 2 + 2 + 2; /* LSE */
+ size += 2; /* EOI */
+ if ((ret = ff_get_encode_buffer(avctx, pkt, size, 0)) < 0)
+ return ret;
+
+ bytestream2_init_writer(&pb, pkt->data, pkt->size);
+
+ /* write our own JPEG header, can't use mjpeg_picture_header */
+ put_marker_byteu(&pb, SOI);
+ put_marker_byteu(&pb, SOF48);
+ bytestream2_put_be16u(&pb, 8 + comps * 3); // header size depends on
components
+ bytestream2_put_byteu(&pb, (avctx->pix_fmt == AV_PIX_FMT_GRAY16) ? 16 :
8); // bpp
+ bytestream2_put_be16u(&pb, avctx->height);
+ bytestream2_put_be16u(&pb, avctx->width);
+ bytestream2_put_byteu(&pb, comps); // components
+ for (i = 1; i <= comps; i++) {
+ bytestream2_put_byteu(&pb, i); // component ID
+ bytestream2_put_byteu(&pb, 0x11); // subsampling: none
+ bytestream2_put_byteu(&pb, 0); // Tiq, used by JPEG-LS ext
+ }
+
+ put_marker_byteu(&pb, SOS);
+ bytestream2_put_be16u(&pb, 6 + comps * 2);
+ bytestream2_put_byteu(&pb, comps);
+ for (i = 1; i <= comps; i++) {
+ bytestream2_put_byteu(&pb, i); // component ID
+ bytestream2_put_byteu(&pb, 0); // mapping index: none
+ }
+ bytestream2_put_byteu(&pb, ctx->pred);
+ bytestream2_put_byteu(&pb, (comps > 1) ? 1 : 0); // interleaving: 0 -
plane, 1 - line
+ bytestream2_put_byteu(&pb, 0); // point transform: none
+
+ ls_store_lse(&state, &pb);
+
/* do escape coding */
- init_get_bits(&gb, pb2.buf, size);
- size -= 7;
- while (get_bits_count(&gb) < size) {
+ init_get_bits(&gb, pb2.buf, size_in_bits);
+ size_in_bits -= 7;
+ while (get_bits_count(&gb) < size_in_bits) {
int v;
v = get_bits(&gb, 8);
bytestream2_put_byte(&pb, v);
@@ -397,15 +414,14 @@ static int encode_picture_ls(AVCodecContext *avctx,
AVPacket *pkt,
bytestream2_put_byte(&pb, v);
}
}
- av_freep(&last);
/* End of image */
put_marker_byte(&pb, EOI);
emms_c();
- pkt->size = bytestream2_tell_p(&pb);
pkt->flags |= AV_PKT_FLAG_KEY;
+ av_shrink_packet(pkt, bytestream2_tell_p(&pb));
