c901896972
Unfortunately, this necessarily involves parsing codec frames to get their durations. Ogg's granule positions indicate the last sample of the last complete frame of the page, so the navigator has to determine the durations of every packet in the page to offset it back to its start. Vorbis is an especially involved codec to determine that for, since it has initial data defining a mapping of indices to big or small block sizes that has to be held onto, and that mapping is preceded by a bunch of conditionally parsed bits. Also, a frame's block size calculation involves the block size of the previous frame for an overlap add. To avoid bringing that complexity directly into LibMedia, we delegate the parsing/calculation to FFmpeg's av_vorbis_parse functions.
64 lines
2.1 KiB
C++
64 lines
2.1 KiB
C++
/*
|
|
* Copyright (c) 2026-present, the Ladybird developers.
|
|
*
|
|
* SPDX-License-Identifier: BSD-2-Clause
|
|
*/
|
|
|
|
#include <LibMedia/Codecs/Opus.h>
|
|
#include <LibMedia/MediaStream.h>
|
|
|
|
namespace Media::Codecs {
|
|
|
|
DecoderErrorOr<u32> Opus::parse_frame_duration_in_samples(MediaStreamCursor& cursor, size_t frame_size)
|
|
{
|
|
if (frame_size == 0)
|
|
return DecoderError::corrupted("Opus frame is too small"sv);
|
|
|
|
// https://datatracker.ietf.org/doc/html/rfc6716#section-3.1
|
|
auto toc_byte = TRY(cursor.read_value<u8>());
|
|
auto configuration_number = (toc_byte >> 3) & 0b1'1111;
|
|
auto packet_code = toc_byte & 0b11;
|
|
|
|
// clang-format off
|
|
constexpr Array frame_durations = {
|
|
10000, 20000, 40000, 60000, // SILK-only NB
|
|
10000, 20000, 40000, 60000, // SILK-only MB
|
|
10000, 20000, 40000, 60000, // SILK-only WB
|
|
10000, 20000, // Hybrid SWB
|
|
10000, 20000, // Hybrid FB
|
|
2500, 5000, 10000, 20000, // CELT-only NB
|
|
2500, 5000, 10000, 20000, // CELT-only WB
|
|
2500, 5000, 10000, 20000, // CELT-only SWB
|
|
2500, 5000, 10000, 20000, // CELT-only FB
|
|
};
|
|
// clang-format on
|
|
|
|
auto frame_duration = frame_durations[configuration_number];
|
|
auto packet_duration = TRY([&] -> DecoderErrorOr<int> {
|
|
switch (packet_code) {
|
|
case 0:
|
|
return frame_duration;
|
|
case 1:
|
|
case 2:
|
|
return frame_duration * 2;
|
|
case 3: {
|
|
if (frame_size == 1)
|
|
return DecoderError::corrupted("Opus frame is too small"sv);
|
|
auto frame_count_byte = TRY(cursor.read_value<u8>());
|
|
auto frame_count = frame_count_byte & 0b11'1111;
|
|
return frame_duration * frame_count;
|
|
}
|
|
default:
|
|
VERIFY_NOT_REACHED();
|
|
}
|
|
}());
|
|
|
|
return packet_duration * 48 / 1000;
|
|
}
|
|
|
|
DecoderErrorOr<AK::Duration> Opus::parse_frame_duration(MediaStreamCursor& cursor, size_t frame_size)
|
|
{
|
|
return AK::Duration::from_time_units(TRY(parse_frame_duration_in_samples(cursor, frame_size)), 1, 48000);
|
|
}
|
|
|
|
}
|