static inline void bs_skip_u(bs_t* b, int n)
{
int i;
for ( i = 0; i < n; i++ )
{
bs_skip_u1( b );
}
}
int pes_read_header(pes_header_t *ph, bs_t *b) {
int PES_packet_start = bs_pos(b);
// we *really* care about bytes 0..19, as we can cheat and manipulate PTS/DTS this way
if (bs_bytes_left(b) < 20)
return 0;
// bytes 0..2
uint32_t pes_packet_start_code = bs_read_u24(b);
if (pes_packet_start_code != PES_PACKET_START_CODE_PREFIX) {
int actually_read = bs_pos(b) - PES_packet_start;
b->p -= actually_read; // undo the read
LOG_WARN_ARGS("PES packet starts with 0x%06X instead of expected start code 0x%06X, skipping it",
pes_packet_start_code, PES_PACKET_START_CODE_PREFIX);
return 0; // bail out! something is fishy!
}
// bytes 3..5
ph->stream_id = bs_read_u8(b);
ph->PES_packet_length = bs_read_u16(b);
if (HAS_PES_HEADER(ph->stream_id)) {
// byte 6
bs_skip_u(b, 2);
ph->PES_scrambling_control = bs_read_u(b, 2);
ph->PES_priority = bs_read_u1(b);
ph->data_alignment_indicator = bs_read_u1(b);
ph->copyright = bs_read_u1(b);
ph->original_or_copy = bs_read_u1(b);
// byte 7
ph->PTS_DTS_flags = bs_read_u(b, 2);
ph->ESCR_flag = bs_read_u1(b);
ph->ES_rate_flag = bs_read_u1(b);
ph->DSM_trick_mode_flag = bs_read_u1(b);
ph->additional_copy_info_flag = bs_read_u1(b);
ph->PES_CRC_flag = bs_read_u1(b);
ph->PES_extension_flag = bs_read_u1(b);
// byte 8
ph->PES_header_data_length = bs_read_u8(b);
int PES_packet_optional_start = bs_pos(b);
// byte 9..14
if (ph->PTS_DTS_flags & PES_PTS_FLAG) {
bs_skip_u(b, 4);
ph->PTS = bs_read_90khz_timestamp(b);
}
// byte 15..19
if (ph->PTS_DTS_flags & PES_DTS_FLAG) {
bs_skip_u(b, 4);
ph->DTS = bs_read_90khz_timestamp(b);
}
if (ph->ESCR_flag) {
bs_skip_u(b, 2);
ph->ESCR_base = bs_read_90khz_timestamp(b);
ph->ESCR_extension = bs_read_u(b, 9);
bs_skip_u1(b);
}
if (ph->ES_rate_flag) {
bs_skip_u1(b);
ph->ES_rate = bs_read_u(b, 22);
bs_skip_u1(b);
}
if (ph->DSM_trick_mode_flag) {
ph->trick_mode_control = bs_read_u(b, 3);
switch (ph->trick_mode_control) {
case PES_DSM_TRICK_MODE_CTL_FAST_FORWARD:
case PES_DSM_TRICK_MODE_CTL_FAST_REVERSE:
ph->field_id = bs_read_u(b, 2);
ph->intra_slice_refresh = bs_read_u1(b);
ph->frequency_truncation = bs_read_u(b, 2);
break;
case PES_DSM_TRICK_MODE_CTL_SLOW_MOTION:
case PES_DSM_TRICK_MODE_CTL_SLOW_REVERSE:
ph->rep_cntrl = bs_read_u(b, 5);
break;
case PES_DSM_TRICK_MODE_CTL_FREEZE_FRAME:
ph->field_id = bs_read_u(b, 2);
bs_skip_u(b, 3);
break;
default:
bs_skip_u(b, 5);
break;
}
}
if (ph->additional_copy_info_flag) {
bs_skip_u1(b);
ph->additional_copy_info = bs_read_u(b, 7);
}
if (ph->PES_CRC_flag) {
ph->previous_PES_packet_CRC = bs_read_u16(b);
}
if (ph->PES_extension_flag) {
ph->PES_private_data_flag = bs_read_u1(b);
ph->pack_header_field_flag = bs_read_u1(b);
ph->program_packet_sequence_counter_flag = bs_read_u1(b);
ph->PSTD_buffer_flag = bs_read_u1(b);
bs_skip_u(b, 3);
ph->PES_extension_flag_2 = bs_read_u1(b);
if (ph->PES_private_data_flag)
bs_read_bytes(b, ph->PES_private_data, 16);
if (ph->pack_header_field_flag) {
// whoever discovers the need for pack_header() is welcome to implement it.
// I haven't.
ph->pack_field_length = bs_read_u8(b);
bs_skip_bytes(b, ph->pack_field_length);
}
if (ph->program_packet_sequence_counter_flag) {
bs_skip_u1(b);
ph->program_packet_sequence_counter = bs_read_u(b, 7);
bs_skip_u1(b);
ph->MPEG1_MPEG2_identifier = bs_read_u1(b);
ph->original_stuff_length = bs_read_u(b, 6);
}
if (ph->PSTD_buffer_flag) {
bs_skip_u(b, 2);
ph->PSTD_buffer_scale = bs_read_u1(b);
ph->PSTD_buffer_size = bs_read_u(b, 13);
}
if (ph->PES_extension_flag_2) {
int PES_extension_field_start = bs_pos(b);
bs_skip_u1(b);
ph->PES_extension_field_length = bs_read_u(b, 7);
ph->stream_id_extension_flag = bs_read_u1(b);
if (!ph->stream_id_extension_flag) {
ph->stream_id_extension = bs_read_u(b, 7);
} else {
bs_skip_u(b, 6);
ph->tref_extension_flag = bs_read_u1(b);
if (ph->tref_extension_flag) {
bs_skip_u(b, 4);
ph->TREF = bs_read_90khz_timestamp(b);
}
}
int PES_extension_bytes_left = bs_pos(b) - PES_extension_field_start;
if (PES_extension_bytes_left > 0)
bs_skip_bytes(b, PES_extension_bytes_left);
}
}
int PES_optional_bytes_read = bs_pos(b) - PES_packet_optional_start;
int stuffing_bytes_len = ph->PES_header_data_length - PES_optional_bytes_read; // if any
if (stuffing_bytes_len > 0)
bs_skip_bytes(b, stuffing_bytes_len);
}
return (bs_pos(b) - PES_packet_start);
}
