[FFmpeg-devel] [PATCH] Kega Game Video (KGV1) decoder

Daniel Verkamp daniel
Tue Mar 2 18:46:38 CET 2010


On Wed, Feb 3, 2010 at 9:02 PM, Michael Niedermayer <michaelni at gmx.at> wrote:
> On Wed, Feb 03, 2010 at 11:49:32AM -0600, Daniel Verkamp wrote:
>> On Wed, Feb 3, 2010 at 10:41 AM, Daniel Verkamp <daniel at drv.nu> wrote:
>> > Hi,
>> >
>> > This is a video capture codec used by the Kega emulator.
>> >
>> > See http://wiki.multimedia.cx/index.php?title=Kega_Video for more information.
>> >
>> > Thanks,
>> > -- Daniel Verkamp
>> >
>>
>> Slightly changed version which (hopefully) fixes endianness issues;
>> still only tested on LE.
>>
> [...]
> are you missing checks for the outpt array size, if so please double
> check your code that there are no further such issues and also try a
> fuzzer
>

Previous version was relying on padded output buffers for this
purpose, but on closer investigation, this was insufficient anyway.
New version has checks for every array/pointer dereference based on
input data.

> [...]
>> + ? ?dst = c->pic.data[0];
>> + ? ?stride = c->pic.linesize[0];
>> + ? ?for (i = 0; i < h; i++)
>> + ? ? ? ?memcpy(dst + i * stride, c->cur + i * w, w * 2);
>
> return your internal buffer dont copy and disable CODEC_CAP_DR1
>

I have attempted to do this, and it seems to work with ffmpeg and
ffplay, but I couldn't find any other codecs that work this way, so it
is mostly trial and error - please double check! Am I correct in
assuming I can just set the output AVFrame's data[0] and linesize[0]
(no get_buffer() use at all), or are there additional required fields?
 The doxygen for AVCodec.decode is nonexistent, so it is not
particularly clear.

Thanks,
-- Daniel Verkamp
-------------- next part --------------
>From c5154318cf7087606f69e1c1aaacc08d2fe47a49 Mon Sep 17 00:00:00 2001
From: Daniel Verkamp <daniel at drv.nu>
Date: Wed, 3 Feb 2010 11:22:03 -0500
Subject: [PATCH] Kega Game Video (KGV1) decoder

---
 Changelog              |    1 +
 doc/general.texi       |    2 +
 libavcodec/Makefile    |    1 +
 libavcodec/allcodecs.c |    1 +
 libavcodec/avcodec.h   |    1 +
 libavcodec/kgv1dec.c   |  178 ++++++++++++++++++++++++++++++++++++++++++++++++
 libavformat/riff.c     |    1 +
 7 files changed, 185 insertions(+), 0 deletions(-)
 create mode 100644 libavcodec/kgv1dec.c

diff --git a/Changelog b/Changelog
index cb276da..104651e 100644
--- a/Changelog
+++ b/Changelog
@@ -61,6 +61,7 @@ version <next>:
 - FFprobe tool
 - AMR-NB decoder
 - RTSP muxer
+- Kega Game Video (KGV1) decoder
 
 
 
diff --git a/doc/general.texi b/doc/general.texi
index 6fed6c3..8f808e8 100644
--- a/doc/general.texi
+++ b/doc/general.texi
@@ -403,6 +403,8 @@ following image formats are supported:
     @tab Used in Interplay .MVE files.
 @item Karl Morton's video codec  @tab     @tab  X
     @tab Codec used in Worms games.
+ at item Kega Game Video (KGV1) @tab      @tab  X
+    @tab Kega emulator screen capture codec.
 @item LCL (LossLess Codec Library) MSZH  @tab     @tab  X
 @item LCL (LossLess Codec Library) ZLIB  @tab  E  @tab  E
 @item LOCO                   @tab     @tab  X
diff --git a/libavcodec/Makefile b/libavcodec/Makefile
index aed14ab..e37cf75 100644
--- a/libavcodec/Makefile
+++ b/libavcodec/Makefile
@@ -167,6 +167,7 @@ OBJS-$(CONFIG_INTERPLAY_VIDEO_DECODER) += interplayvideo.o
 OBJS-$(CONFIG_JPEGLS_DECODER)          += jpeglsdec.o jpegls.o \
                                           mjpegdec.o mjpeg.o
 OBJS-$(CONFIG_JPEGLS_ENCODER)          += jpeglsenc.o jpegls.o
+OBJS-$(CONFIG_KGV1_DECODER)            += kgv1dec.o
 OBJS-$(CONFIG_KMVC_DECODER)            += kmvc.o
 OBJS-$(CONFIG_LJPEG_ENCODER)           += ljpegenc.o mjpegenc.o mjpeg.o \
                                           mpegvideo_enc.o motion_est.o  \
diff --git a/libavcodec/allcodecs.c b/libavcodec/allcodecs.c
index f0a93a2..5dbf1dc 100644
--- a/libavcodec/allcodecs.c
+++ b/libavcodec/allcodecs.c
@@ -122,6 +122,7 @@ void avcodec_register_all(void)
     REGISTER_DECODER (INDEO5, indeo5);
     REGISTER_DECODER (INTERPLAY_VIDEO, interplay_video);
     REGISTER_ENCDEC  (JPEGLS, jpegls);
+    REGISTER_DECODER (KGV1, kgv1);
     REGISTER_DECODER (KMVC, kmvc);
     REGISTER_ENCODER (LJPEG, ljpeg);
     REGISTER_DECODER (LOCO, loco);
diff --git a/libavcodec/avcodec.h b/libavcodec/avcodec.h
index 31569d3..ea2a886 100644
--- a/libavcodec/avcodec.h
+++ b/libavcodec/avcodec.h
@@ -206,6 +206,7 @@ enum CodecID {
     CODEC_ID_BINKVIDEO,
     CODEC_ID_IFF_ILBM,
     CODEC_ID_IFF_BYTERUN1,
+    CODEC_ID_KGV1,
 
     /* various PCM "codecs" */
     CODEC_ID_PCM_S16LE= 0x10000,
diff --git a/libavcodec/kgv1dec.c b/libavcodec/kgv1dec.c
new file mode 100644
index 0000000..c800bd4
--- /dev/null
+++ b/libavcodec/kgv1dec.c
@@ -0,0 +1,178 @@
+/*
+ * Kega Game Video (KGV1) decoder
+ * Copyright (c) 2010 Daniel Verkamp
+ *
+ * This file is part of FFmpeg.
+ *
+ * FFmpeg is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * FFmpeg is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with FFmpeg; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+/**
+ * @file libavcodec/kgv1dec.c
+ * Kega Game Video decoder
+ */
+
+#include "libavutil/intreadwrite.h"
+#include "avcodec.h"
+
+typedef struct {
+    AVCodecContext *avctx;
+    AVFrame pic;
+    uint16_t *prev, *cur;
+} KgvContext;
+
+static int decode_frame(AVCodecContext *avctx, void *data, int *data_size, AVPacket *avpkt)
+{
+    const uint8_t *buf = avpkt->data;
+    const uint8_t *buf_end = buf + avpkt->size;
+    KgvContext * const c = avctx->priv_data;
+    int offsets[7];
+    uint16_t *out, *prev;
+    int outcnt = 0, maxcnt;
+    int w, h, i;
+
+    if (avpkt->size < 2)
+        return -1;
+
+    w = (buf[0] + 1) * 8;
+    h = (buf[1] + 1) * 8;
+    buf += 2;
+
+    if (avcodec_check_dimensions(avctx, w, h))
+        return -1;
+
+    if (w != avctx->width || h != avctx->height)
+        avcodec_set_dimensions(avctx, w, h);
+
+    maxcnt = w * h;
+
+    c->pic.buffer_hints = FF_BUFFER_HINTS_VALID | FF_BUFFER_HINTS_PRESERVE
+                        | FF_BUFFER_HINTS_REUSABLE;
+
+    out = av_realloc(c->cur, w * h * 2);
+    if (!out)
+        return -1;
+    c->cur = out;
+
+    prev = av_realloc(c->prev, w * h * 2);
+    if (!prev)
+        return -1;
+    c->prev = prev;
+
+    for (i = 0; i < 7; i++)
+        offsets[i] = -1;
+
+    while (outcnt < maxcnt && buf_end - 2 > buf) {
+        int code = AV_RL16(buf);
+        buf += 2;
+        if (!(code & 0x8000)) {
+            out[outcnt++] = code; // rgb555 pixel coded directly
+        } else {
+            if ((code & 0x6000) == 0x6000) {
+                // copy from previous frame
+                int count = (code & 0x3FF) + 3;
+                int oidx  = (code >>   10) & 7;
+                int start;
+
+                if (offsets[oidx] == -1) {
+                    if (buf_end - 3 < buf)
+                        break;
+                    offsets[oidx] = AV_RL24(buf);
+                    if (offsets[oidx] < 0) {
+                        av_log(avctx, AV_LOG_ERROR, "negative offset\n");
+                        offsets[oidx] = 0;
+                        break;
+                    }
+                    buf += 3;
+                }
+
+                start = (outcnt + offsets[oidx]) % maxcnt;
+
+                if (maxcnt - outcnt < count || maxcnt - start < count)
+                    break;
+
+                for (i = 0; i < count; i++)
+                    out[outcnt++] = prev[start + i];
+
+            } else {
+                // copy from earlier in this frame
+                int count;
+                int offset = (code & 0x1FFF) + 1;
+                uint16_t *inp;
+                if (!(code & 0x6000)) {
+                    count = 2;
+                } else if ((code & 0x6000) == 0x2000) {
+                    count = 3;
+                } else {
+                    if (buf_end - 1 < buf)
+                        break;
+                    count = *buf++ + 4;
+                }
+
+                if (outcnt - offset < 0 || maxcnt - outcnt < count)
+                    break;
+
+                inp = out + outcnt - offset;
+                for (i = 0; i < count; i++)
+                    out[outcnt++] = inp[i];
+            }
+        }
+    }
+
+    if (outcnt - maxcnt)
+        av_log(avctx, AV_LOG_DEBUG, "frame finished with %d diff\n", outcnt - maxcnt);
+
+    c->pic.data[0]     = (uint8_t *)c->cur;
+    c->pic.linesize[0] = w * 2;
+
+    *data_size = sizeof(AVFrame);
+    *(AVFrame*)data = c->pic;
+
+    FFSWAP(uint16_t *, c->cur, c->prev);
+
+    return avpkt->size;
+}
+
+static av_cold int decode_init(AVCodecContext *avctx)
+{
+    KgvContext * const c = avctx->priv_data;
+
+    c->avctx = avctx;
+    avctx->pix_fmt = PIX_FMT_RGB555;
+
+    return 0;
+}
+
+static av_cold int decode_end(AVCodecContext *avctx)
+{
+    KgvContext * const c = avctx->priv_data;
+
+    av_freep(&c->cur);
+    av_freep(&c->prev);
+
+    return 0;
+}
+
+AVCodec kgv1_decoder = {
+    "kgv1",
+    CODEC_TYPE_VIDEO,
+    CODEC_ID_KGV1,
+    sizeof(KgvContext),
+    decode_init,
+    NULL,
+    decode_end,
+    decode_frame,
+    .long_name = NULL_IF_CONFIG_SMALL("Kega Game Video"),
+};
diff --git a/libavformat/riff.c b/libavformat/riff.c
index 0a3bc95..f241421 100644
--- a/libavformat/riff.c
+++ b/libavformat/riff.c
@@ -240,6 +240,7 @@ const AVCodecTag ff_codec_bmp_tags[] = {
     { CODEC_ID_AURA,         MKTAG('A', 'U', 'R', 'A') },
     { CODEC_ID_AURA2,        MKTAG('A', 'U', 'R', '2') },
     { CODEC_ID_DPX,          MKTAG('d', 'p', 'x', ' ') },
+    { CODEC_ID_KGV1,         MKTAG('K', 'G', 'V', '1') },
     { CODEC_ID_NONE,         0 }
 };
 
-- 
1.6.6.1



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