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cbs_av1: Fix reading of overlong uvlc codes

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The specification allows 2^32-1 to be encoded as any number of zeroes
greater than 31, followed by a one.  This previously failed because the
trace code would overflow the array containing the string representation
of the bits if there were more than 63 zeroes.  Fix that by splitting the
trace output into batches, and at the same time move it out of the default
path.

(While this seems likely to be a specification error, libaom does support
it so we probably should as well.)

From a test case by keval shah <skeval65@gmail.com>.

Reviewed-by: Michael Niedermayer <michael@niedermayer.cc>
This commit is contained in:
Mark Thompson 2018-12-02 20:49:24 +00:00
parent dfd656632e
commit b97a4b6588
1 changed files with 40 additions and 18 deletions
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58
libavcodec/cbs_av1.c
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@ -29,45 +29,67 @@ static int cbs_av1_read_uvlc(CodedBitstreamContext *ctx, GetBitContext *gbc,
const char *name, uint32_t *write_to,
uint32_t range_min, uint32_t range_max)
{
uint32_t value;
int position, zeroes, i, j;
char bits[65];
uint32_t zeroes, bits_value, value;
int position;
if (ctx->trace_enable)
position = get_bits_count(gbc);
zeroes = i = 0;
zeroes = 0;
while (1) {
if (get_bits_left(gbc) < zeroes + 1) {
if (get_bits_left(gbc) < 1) {
av_log(ctx->log_ctx, AV_LOG_ERROR, "Invalid uvlc code at "
"%s: bitstream ended.\n", name);
return AVERROR_INVALIDDATA;
}
if (get_bits1(gbc)) {
bits[i++] = '1';
if (get_bits1(gbc))
break;
} else {
bits[i++] = '0';
++zeroes;
}
++zeroes;
}
if (zeroes >= 32) {
value = MAX_UINT_BITS(32);
} else {
value = get_bits_long(gbc, zeroes);
if (get_bits_left(gbc) < zeroes) {
av_log(ctx->log_ctx, AV_LOG_ERROR, "Invalid uvlc code at "
"%s: bitstream ended.\n", name);
return AVERROR_INVALIDDATA;
}
for (j = 0; j < zeroes; j++)
bits[i++] = (value >> (zeroes - j - 1) & 1) ? '1' : '0';
value += (1 << zeroes) - 1;
bits_value = get_bits_long(gbc, zeroes);
value = bits_value + (UINT32_C(1) << zeroes) - 1;
}
if (ctx->trace_enable) {
char bits[65];
int i, j, k;
if (zeroes >= 32) {
while (zeroes > 32) {
k = FFMIN(zeroes - 32, 32);
for (i = 0; i < k; i++)
bits[i] = '0';
bits[i] = 0;
ff_cbs_trace_syntax_element(ctx, position, name,
NULL, bits, 0);
zeroes -= k;
position += k;
}
}
for (i = 0; i < zeroes; i++)
bits[i] = '0';
bits[i++] = '1';
if (zeroes < 32) {
for (j = 0; j < zeroes; j++)
bits[i++] = (bits_value >> (zeroes - j - 1) & 1) ? '1' : '0';
}
bits[i] = 0;
ff_cbs_trace_syntax_element(ctx, position, name, NULL,
bits, value);
ff_cbs_trace_syntax_element(ctx, position, name,
NULL, bits, value);
}
if (value < range_min || value > range_max) {