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jpegdec: don't overwrite the last valid line

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If the the height is not a multiple of the macro block size then the memory
of the last line is reused for all extra lines. This is no problem if the
last line is duplicated properly. However, if the extra lines are not
initialized properly during encoding, then the last visible line is
overwritten with undefined data.
Use a extra buffer to avoid this problem.
This commit is contained in:
Michael Olbrich 2018-11-07 09:00:02 +01:00
parent 9dc1a32d5a
commit 0b25487cd1
2 changed files with 16 additions and 3 deletions
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16
ext/jpeg/gstjpegdec.c
View file

@ -894,6 +894,12 @@ gst_jpeg_dec_decode_direct (GstJpegDec * dec, GstVideoFrame * frame,
}
}
if (height % (v_samp[0] * DCTSIZE) && (dec->scratch_size < stride[0])) {
g_free (dec->scratch);
dec->scratch = g_malloc (stride[0]);
dec->scratch_size = stride[0];
}
/* let jpeglib decode directly into our final buffer */
GST_DEBUG_OBJECT (dec, "decoding directly into output buffer");
@ -902,7 +908,7 @@ gst_jpeg_dec_decode_direct (GstJpegDec * dec, GstVideoFrame * frame,
/* Y */
line[0][j] = base[0] + (i + j) * stride[0];
if (G_UNLIKELY (line[0][j] > last[0]))
line[0][j] = last[0];
line[0][j] = dec->scratch;
/* U */
if (v_samp[1] == v_samp[0]) {
line[1][j] = base[1] + ((i + j) / 2) * stride[1];
@ -910,7 +916,7 @@ gst_jpeg_dec_decode_direct (GstJpegDec * dec, GstVideoFrame * frame,
line[1][j] = base[1] + ((i / 2) + j) * stride[1];
}
if (G_UNLIKELY (line[1][j] > last[1]))
line[1][j] = last[1];
line[1][j] = dec->scratch;
/* V */
if (v_samp[2] == v_samp[0]) {
line[2][j] = base[2] + ((i + j) / 2) * stride[2];
@ -918,7 +924,7 @@ gst_jpeg_dec_decode_direct (GstJpegDec * dec, GstVideoFrame * frame,
line[2][j] = base[2] + ((i / 2) + j) * stride[2];
}
if (G_UNLIKELY (line[2][j] > last[2]))
line[2][j] = last[2];
line[2][j] = dec->scratch;
}
lines = jpeg_read_raw_data (&dec->cinfo, line, v_samp[0] * DCTSIZE);
@ -1555,5 +1561,9 @@ gst_jpeg_dec_stop (GstVideoDecoder * bdec)
gst_jpeg_dec_free_buffers (dec);
g_free (dec->scratch);
dec->scratch = NULL;
dec->scratch_size = 0;
return TRUE;
}

3
ext/jpeg/gstjpegdec.h
View file

@ -90,6 +90,9 @@ struct _GstJpegDec {
/* arrays for indirect decoding */
gboolean idr_width_allocated;
guchar *idr_y[16],*idr_u[16],*idr_v[16];
/* scratch buffer for direct decoding overflow */
guchar *scratch;
guint scratch_size;
/* current (parsed) image size */
guint rem_img_len;
};