static vpx_codec_err_t vp9_peek_si(const uint8_t *data, unsigned int data_sz,
vpx_codec_stream_info_t *si) {
if (data_sz <= 8) return VPX_CODEC_UNSUP_BITSTREAM;
if (data + data_sz <= data) return VPX_CODEC_INVALID_PARAM;
si->is_kf = 0;
si->w = si->h = 0;
{
struct vp9_read_bit_buffer rb = { data, data + data_sz, 0, NULL, NULL };
const int frame_marker = vp9_rb_read_literal(&rb, 2);
const int version = vp9_rb_read_bit(&rb);
(void) vp9_rb_read_bit(&rb); // unused version bit
if (frame_marker != VP9_FRAME_MARKER)
return VPX_CODEC_UNSUP_BITSTREAM;
if (version > 1) return VPX_CODEC_UNSUP_BITSTREAM;
if (vp9_rb_read_bit(&rb)) { // show an existing frame
return VPX_CODEC_OK;
}
si->is_kf = !vp9_rb_read_bit(&rb);
if (si->is_kf) {
const int sRGB = 7;
int colorspace;
rb.bit_offset += 1; // show frame
rb.bit_offset += 1; // error resilient
if (vp9_rb_read_literal(&rb, 8) != VP9_SYNC_CODE_0 ||
vp9_rb_read_literal(&rb, 8) != VP9_SYNC_CODE_1 ||
vp9_rb_read_literal(&rb, 8) != VP9_SYNC_CODE_2) {
return VPX_CODEC_UNSUP_BITSTREAM;
}
colorspace = vp9_rb_read_literal(&rb, 3);
if (colorspace != sRGB) {
rb.bit_offset += 1; // [16,235] (including xvycc) vs [0,255] range
if (version == 1) {
rb.bit_offset += 2; // subsampling x/y
rb.bit_offset += 1; // has extra plane
}
} else {
if (version == 1) {
rb.bit_offset += 1; // has extra plane
} else {
// RGB is only available in version 1
return VPX_CODEC_UNSUP_BITSTREAM;
}
}
// TODO(jzern): these are available on non-keyframes in intra only mode.
si->w = vp9_rb_read_literal(&rb, 16) + 1;
si->h = vp9_rb_read_literal(&rb, 16) + 1;
}
}
return VPX_CODEC_OK;
}
static int parse_bitdepth_colorspace_sampling(
BITSTREAM_PROFILE profile, struct vp9_read_bit_buffer *rb) {
vpx_color_space_t color_space;
if (profile >= PROFILE_2)
rb->bit_offset += 1; // Bit-depth 10 or 12.
color_space = (vpx_color_space_t)vp9_rb_read_literal(rb, 3);
if (color_space != VPX_CS_SRGB) {
rb->bit_offset += 1; // [16,235] (including xvycc) vs [0,255] range.
if (profile == PROFILE_1 || profile == PROFILE_3) {
rb->bit_offset += 2; // subsampling x/y.
rb->bit_offset += 1; // unused.
}
} else {
if (profile == PROFILE_1 || profile == PROFILE_3) {
rb->bit_offset += 1; // unused
} else {
// RGB is only available in version 1.
return 0;
}
}
return 1;
}
static int decode_unsigned_max(struct vp9_read_bit_buffer *rb, int max) {
const int data = vp9_rb_read_literal(rb, get_unsigned_bits(max));
return data > max ? max : data;
}
static vpx_codec_err_t decoder_peek_si_internal(const uint8_t *data,
unsigned int data_sz,
vpx_codec_stream_info_t *si,
int *is_intra_only,
vpx_decrypt_cb decrypt_cb,
void *decrypt_state) {
int intra_only_flag = 0;
uint8_t clear_buffer[9];
if (data + data_sz <= data)
return VPX_CODEC_INVALID_PARAM;
si->is_kf = 0;
si->w = si->h = 0;
if (decrypt_cb) {
data_sz = MIN(sizeof(clear_buffer), data_sz);
decrypt_cb(decrypt_state, data, clear_buffer, data_sz);
data = clear_buffer;
}
{
int show_frame;
int error_resilient;
struct vp9_read_bit_buffer rb = { data, data + data_sz, 0, NULL, NULL };
const int frame_marker = vp9_rb_read_literal(&rb, 2);
const BITSTREAM_PROFILE profile = vp9_read_profile(&rb);
if (frame_marker != VP9_FRAME_MARKER)
return VPX_CODEC_UNSUP_BITSTREAM;
if (profile >= MAX_PROFILES)
return VPX_CODEC_UNSUP_BITSTREAM;
if ((profile >= 2 && data_sz <= 1) || data_sz < 1)
return VPX_CODEC_UNSUP_BITSTREAM;
if (vp9_rb_read_bit(&rb)) { // show an existing frame
vp9_rb_read_literal(&rb, 3); // Frame buffer to show.
return VPX_CODEC_OK;
}
if (data_sz <= 8)
return VPX_CODEC_UNSUP_BITSTREAM;
si->is_kf = !vp9_rb_read_bit(&rb);
show_frame = vp9_rb_read_bit(&rb);
error_resilient = vp9_rb_read_bit(&rb);
if (si->is_kf) {
if (!vp9_read_sync_code(&rb))
return VPX_CODEC_UNSUP_BITSTREAM;
if (!parse_bitdepth_colorspace_sampling(profile, &rb))
return VPX_CODEC_UNSUP_BITSTREAM;
vp9_read_frame_size(&rb, (int *)&si->w, (int *)&si->h);
} else {
intra_only_flag = show_frame ? 0 : vp9_rb_read_bit(&rb);
rb.bit_offset += error_resilient ? 0 : 2; // reset_frame_context
if (intra_only_flag) {
if (!vp9_read_sync_code(&rb))
return VPX_CODEC_UNSUP_BITSTREAM;
if (profile > PROFILE_0) {
if (!parse_bitdepth_colorspace_sampling(profile, &rb))
return VPX_CODEC_UNSUP_BITSTREAM;
}
rb.bit_offset += REF_FRAMES; // refresh_frame_flags
vp9_read_frame_size(&rb, (int *)&si->w, (int *)&si->h);
}
}
}
if (is_intra_only != NULL)
*is_intra_only = intra_only_flag;
return VPX_CODEC_OK;
}