4xm: replace forcing EMU_EDGE by a copy

The decoder currently sets CODEC_FLAG_EMU_EDGE and relies on
get_buffer2() to always provide buffers with linesize == 2 * width.
This is wrong, since we place no such restriction on get_buffer2()
implementations.

Fix this by decoding into internal buffers and copying them to output
frames. Since this is a very obscure decoder, the performance hit should
not be an issue.

libavcodec/4xm.c

@@ -25,6 +25,7 @@
  */
 
 #include "libavutil/frame.h"
+#include "libavutil/imgutils.h"
 #include "libavutil/intreadwrite.h"
 #include "avcodec.h"
 #include "bytestream.h"
@@ -129,7 +130,8 @@ typedef struct CFrameBuffer {
 typedef struct FourXContext {
     AVCodecContext *avctx;
     DSPContext dsp;
-    AVFrame *last_picture;
+    uint16_t *frame_buffer;
+    uint16_t *last_frame_buffer;
     GetBitContext pre_gb;          ///< ac/dc prefix
     GetBitContext gb;
     GetByteContext g;
@@ -339,7 +341,7 @@ static int decode_p_block(FourXContext *f, uint16_t *dst, uint16_t *src,
     int code        = get_vlc2(&f->gb,
                                block_type_vlc[1 - (f->version > 1)][index].table,
                                BLOCK_TYPE_VLC_BITS, 1);
-    uint16_t *start = (uint16_t *)f->last_picture->data[0];
+    uint16_t *start = f->last_frame_buffer;
     uint16_t *end   = start + stride * (f->avctx->height - h + 1) - (1 << log2w);
     int ret;
     int scale   = 1;
@@ -395,30 +397,18 @@ static int decode_p_block(FourXContext *f, uint16_t *dst, uint16_t *src,
     return 0;
 }
 
-static int decode_p_frame(FourXContext *f, AVFrame *frame,
-                          const uint8_t *buf, int length)
+static int decode_p_frame(FourXContext *f, const uint8_t *buf, int length)
 {
     int x, y;
     const int width  = f->avctx->width;
     const int height = f->avctx->height;
-    uint16_t *dst    = (uint16_t *)frame->data[0];
-    const int stride =             frame->linesize[0] >> 1;
+    uint16_t *dst    = f->frame_buffer;
     uint16_t *src;
     unsigned int bitstream_size, bytestream_size, wordstream_size, extra,
                  bytestream_offset, wordstream_offset;
     int ret;
 
-    if (!f->last_picture->data[0]) {
-        if ((ret = ff_get_buffer(f->avctx, f->last_picture,
-                                 AV_GET_BUFFER_FLAG_REF)) < 0) {
-            av_log(f->avctx, AV_LOG_ERROR, "get_buffer() failed\n");
-            return ret;
-        }
-        memset(f->last_picture->data[0], 0,
-               f->avctx->height * FFABS(f->last_picture->linesize[0]));
-    }
-
-    src = (uint16_t *)f->last_picture->data[0];
+    src = f->last_frame_buffer;
 
     if (f->version > 1) {
         if (length < 20)
@@ -461,14 +451,14 @@ static int decode_p_frame(FourXContext *f, AVFrame *frame,
     bytestream2_init(&f->g, buf + bytestream_offset,
                      length - bytestream_offset);
 
-    init_mv(f, frame->linesize[0]);
+    init_mv(f, width * 2);
 
     for (y = 0; y < height; y += 8) {
         for (x = 0; x < width; x += 8)
-            if ((ret = decode_p_block(f, dst + x, src + x, 3, 3, stride)) < 0)
+            if ((ret = decode_p_block(f, dst + x, src + x, 3, 3, width)) < 0)
                 return ret;
-        src += 8 * stride;
-        dst += 8 * stride;
+        src += 8 * width;
+        dst += 8 * width;
     }
 
     return 0;
@@ -521,12 +511,12 @@ static int decode_i_block(FourXContext *f, int16_t *block)
     return 0;
 }
 
-static inline void idct_put(FourXContext *f, AVFrame *frame, int x, int y)
+static inline void idct_put(FourXContext *f, int x, int y)
 {
     int16_t (*block)[64] = f->block;
-    int stride           = frame->linesize[0] >> 1;
+    int stride           = f->avctx->width;
     int i;
-    uint16_t *dst = ((uint16_t*)frame->data[0]) + y * stride + x;
+    uint16_t *dst = f->frame_buffer + y * stride + x;
 
     for (i = 0; i < 4; i++) {
         block[i][0] += 0x80 * 8 * 8;
@@ -683,14 +673,13 @@ static int mix(int c0, int c1)
     return red / 3 * 1024 + green / 3 * 32 + blue / 3;
 }
 
-static int decode_i2_frame(FourXContext *f, AVFrame *frame, const uint8_t *buf, int length)
+static int decode_i2_frame(FourXContext *f, const uint8_t *buf, int length)
 {
     int x, y, x2, y2;
     const int width  = f->avctx->width;
     const int height = f->avctx->height;
     const int mbs    = (FFALIGN(width, 16) >> 4) * (FFALIGN(height, 16) >> 4);
-    uint16_t *dst    = (uint16_t*)frame->data[0];
-    const int stride =            frame->linesize[0]>>1;
+    uint16_t *dst    = f->frame_buffer;
     GetByteContext g3;
 
     if (length < mbs * 8) {
@@ -718,18 +707,18 @@ static int decode_i2_frame(FourXContext *f, AVFrame *frame, const uint8_t *buf,
             for (y2 = 0; y2 < 16; y2++) {
                 for (x2 = 0; x2 < 16; x2++) {
                     int index = 2 * (x2 >> 2) + 8 * (y2 >> 2);
-                    dst[y2 * stride + x2] = color[(bits >> index) & 3];
+                    dst[y2 * width + x2] = color[(bits >> index) & 3];
                 }
             }
             dst += 16;
         }
-        dst += 16 * stride - x;
+        dst += 16 * width - x;
     }
 
     return 0;
 }
 
-static int decode_i_frame(FourXContext *f, AVFrame *frame, const uint8_t *buf, int length)
+static int decode_i_frame(FourXContext *f, const uint8_t *buf, int length)
 {
     int x, y, ret;
     const int width  = f->avctx->width;
@@ -785,7 +774,7 @@ static int decode_i_frame(FourXContext *f, AVFrame *frame, const uint8_t *buf, i
             if ((ret = decode_i_mb(f)) < 0)
                 return ret;
 
-            idct_put(f, frame, x, y);
+            idct_put(f, x, y);
         }
     }
 
@@ -882,25 +871,23 @@ static int decode_frame(AVCodecContext *avctx, void *data,
         frame_size = buf_size - 12;
     }
 
-    // alternatively we would have to use our own buffer management
-    avctx->flags |= CODEC_FLAG_EMU_EDGE;
 
-    if ((ret = ff_get_buffer(avctx, picture, AV_GET_BUFFER_FLAG_REF)) < 0) {
+    if ((ret = ff_get_buffer(avctx, picture, 0)) < 0) {
         av_log(avctx, AV_LOG_ERROR, "get_buffer() failed\n");
         return ret;
     }
 
     if (frame_4cc == AV_RL32("ifr2")) {
         picture->pict_type = AV_PICTURE_TYPE_I;
-        if ((ret = decode_i2_frame(f, picture, buf - 4, frame_size + 4)) < 0)
+        if ((ret = decode_i2_frame(f, buf - 4, frame_size + 4)) < 0)
             return ret;
     } else if (frame_4cc == AV_RL32("ifrm")) {
         picture->pict_type = AV_PICTURE_TYPE_I;
-        if ((ret = decode_i_frame(f, picture, buf, frame_size)) < 0)
+        if ((ret = decode_i_frame(f, buf, frame_size)) < 0)
             return ret;
     } else if (frame_4cc == AV_RL32("pfrm") || frame_4cc == AV_RL32("pfr2")) {
         picture->pict_type = AV_PICTURE_TYPE_P;
-        if ((ret = decode_p_frame(f, picture, buf, frame_size)) < 0)
+        if ((ret = decode_p_frame(f, buf, frame_size)) < 0)
             return ret;
     } else if (frame_4cc == AV_RL32("snd_")) {
         av_log(avctx, AV_LOG_ERROR, "ignoring snd_ chunk length:%d\n",
@@ -912,9 +899,11 @@ static int decode_frame(AVCodecContext *avctx, void *data,
 
     picture->key_frame = picture->pict_type == AV_PICTURE_TYPE_I;
 
-    av_frame_unref(f->last_picture);
-    if ((ret = av_frame_ref(f->last_picture, picture)) < 0)
-        return ret;
+    av_image_copy_plane(picture->data[0], picture->linesize[0],
+                        (const uint8_t*)f->frame_buffer,  avctx->width * 2,
+                        avctx->width * 2, avctx->height);
+    FFSWAP(uint16_t *, f->frame_buffer, f->last_frame_buffer);
+
     *got_frame = 1;
 
     emms_c();
@@ -922,15 +911,45 @@ static int decode_frame(AVCodecContext *avctx, void *data,
     return buf_size;
 }
 
+static av_cold int decode_end(AVCodecContext *avctx)
+{
+    FourXContext * const f = avctx->priv_data;
+    int i;
+
+    av_freep(&f->frame_buffer);
+    av_freep(&f->last_frame_buffer);
+    av_freep(&f->bitstream_buffer);
+    f->bitstream_buffer_size = 0;
+    for (i = 0; i < CFRAME_BUFFER_COUNT; i++) {
+        av_freep(&f->cfrm[i].data);
+        f->cfrm[i].allocated_size = 0;
+    }
+    ff_free_vlc(&f->pre_vlc);
+
+    return 0;
+}
+
 static av_cold int decode_init(AVCodecContext *avctx)
 {
     FourXContext * const f = avctx->priv_data;
+    int ret;
 
     if (avctx->extradata_size != 4 || !avctx->extradata) {
         av_log(avctx, AV_LOG_ERROR, "extradata wrong or missing\n");
         return AVERROR_INVALIDDATA;
     }
 
+    ret = av_image_check_size(avctx->width, avctx->height, 0, avctx);
+    if (ret < 0)
+        return ret;
+
+    f->frame_buffer      = av_mallocz(avctx->width * avctx->height * 2);
+    f->last_frame_buffer = av_mallocz(avctx->width * avctx->height * 2);
+    if (!f->frame_buffer || !f->last_frame_buffer) {
+        decode_end(avctx);
+        return AVERROR(ENOMEM);
+    }
+
     f->version = AV_RL32(avctx->extradata) >> 16;
     ff_dsputil_init(&f->dsp, avctx);
     f->avctx = avctx;
@@ -941,28 +960,6 @@ static av_cold int decode_init(AVCodecContext *avctx)
     else
         avctx->pix_fmt = AV_PIX_FMT_BGR555;
 
-    f->last_picture = av_frame_alloc();
-    if (!f->last_picture)
-        return AVERROR(ENOMEM);
-
-    return 0;
-}
-
-
-static av_cold int decode_end(AVCodecContext *avctx)
-{
-    FourXContext * const f = avctx->priv_data;
-    int i;
-
-    av_freep(&f->bitstream_buffer);
-    f->bitstream_buffer_size = 0;
-    for (i = 0; i < CFRAME_BUFFER_COUNT; i++) {
-        av_freep(&f->cfrm[i].data);
-        f->cfrm[i].allocated_size = 0;
-    }
-    ff_free_vlc(&f->pre_vlc);
-    av_frame_free(&f->last_picture);
-
     return 0;
 }