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libobs: Add caption support for HEVC

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Add embedded caption support for HEVC by slightly modifying the H.264
SEI to be an HEVC SEI (2 byte SEI NAL header).
This commit is contained in:
JoHn BoWeRs
2024-03-13 13:55:00 -06:00
committed by Lain
parent f9bc9a8b12
commit 33eb95c274
1 changed files with 63 additions and 6 deletions
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libobs/obs-output.c
+63 -6
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@@ -1520,6 +1520,7 @@ static bool add_caption(struct obs_output *output, struct encoder_packet *out)
size_t size;
long ref = 1;
bool avc = false;
bool hevc = false;
/* Instead of exiting early for unsupported codecs, we will continue
* processing to allow the freeing of caption data even if the captions
@@ -1527,6 +1528,10 @@ static bool add_caption(struct obs_output *output, struct encoder_packet *out)
* the given codec. */
if (strcmp(out->encoder->info.codec, "h264") == 0) {
avc = true;
#ifdef ENABLE_HEVC
} else if (strcmp(out->encoder->info.codec, "hevc") == 0) {
hevc = true;
#endif
}
DARRAY(uint8_t) out_data;
@@ -1543,6 +1548,31 @@ static bool add_caption(struct obs_output *output, struct encoder_packet *out)
return false;
}
#ifdef ENABLE_HEVC
uint8_t hevc_nal_header[2];
if (hevc) {
size_t nal_header_index_start = 4;
// Skip past the annex-b start code
if (memcmp(out->data, nal_start + 1, 3) == 0) {
nal_header_index_start = 3;
} else if (memcmp(out->data, nal_start, 4) == 0) {
nal_header_index_start = 4;
} else {
/* We shouldn't ever see this unless we start getting
* packets without annex-b start codes. */
blog(LOG_DEBUG,
"Annex-B start code not found. We may not "
"generate a valid HEVC NAL unit header "
"for our caption");
return false;
}
/* We will use the same 2 byte NAL unit header for the CC SEI,
* but swap the NAL types out. */
hevc_nal_header[0] = out->data[nal_header_index_start];
hevc_nal_header[1] = out->data[nal_header_index_start + 1];
}
#endif
sei_init(&sei, 0.0);
da_init(out_data);
@@ -1606,13 +1636,40 @@ static bool add_caption(struct obs_output *output, struct encoder_packet *out)
ctrack->caption_head = next;
}
if (avc) {
if (avc || hevc) {
data = malloc(sei_render_size(&sei));
size = sei_render(&sei, data);
/* TODO: SEI should come after AUD/SPS/PPS,
* but before any VCL */
da_push_back_array(out_data, nal_start, 4);
da_push_back_array(out_data, data, size);
if (avc) {
/* TODO: SEI should come after AUD/SPS/PPS,
* but before any VCL */
da_push_back_array(out_data, nal_start, 4);
da_push_back_array(out_data, data, size);
#ifdef ENABLE_HEVC
} else if (hevc) {
/* Only first NAL, VPS/PPS/SPS should use the 4 byte
start code, SEIs use 3 byte version */
da_push_back_array(out_data, nal_start + 1, 3);
/* nal_unit_header( ) {
* forbidden_zero_bit f(1)
* nal_unit_type u(6)
* nuh_layer_id u(6)
* nuh_temporal_id_plus1 u(3)
* }
*/
const uint8_t prefix_sei_nal_type = 39;
/* The first bit is always 0, so we just need to
* save the last bit off the original header and
* add the SEI NAL type. */
uint8_t first_byte = (prefix_sei_nal_type << 1) |
(0x01 & hevc_nal_header[0]);
hevc_nal_header[0] = first_byte;
/* The HEVC NAL unit header is 2 byte instead of
* one, otherwise everything else is the
* same. */
da_push_back_array(out_data, hevc_nal_header, 2);
da_push_back_array(out_data, &data[1], size - 1);
#endif
}
free(data);
}
@@ -1622,7 +1679,7 @@ static bool add_caption(struct obs_output *output, struct encoder_packet *out)
out->data = (uint8_t *)out_data.array + sizeof(ref);
out->size = out_data.num - sizeof(ref);
sei_free(&sei);
if (avc) {
if (avc || hevc) {
return true;
}
return false;