blob: 1e706faba4e56561a4d714dd1ce47fffd5d751da [file] [log] [blame]
// Copyright 2014 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#include "media/base/audio_discard_helper.h"
#include <algorithm>
#include "base/logging.h"
#include "media/base/audio_buffer.h"
namespace media {
static void WarnOnNonMonotonicTimestamps(base::TimeDelta last_timestamp,
base::TimeDelta current_timestamp) {
if (last_timestamp == kNoTimestamp || last_timestamp <= current_timestamp)
return;
const base::TimeDelta diff = current_timestamp - last_timestamp;
DLOG(WARNING) << "Input timestamps are not monotonically increasing! "
<< " ts " << current_timestamp.InMicroseconds() << " us"
<< " diff " << diff.InMicroseconds() << " us";
}
AudioDiscardHelper::AudioDiscardHelper(int sample_rate,
size_t decoder_delay,
bool delayed_discard)
: sample_rate_(sample_rate),
decoder_delay_(decoder_delay),
timestamp_helper_(sample_rate_),
discard_frames_(0),
last_input_timestamp_(kNoTimestamp),
delayed_discard_(delayed_discard),
delayed_end_discard_(0) {
DCHECK_GT(sample_rate_, 0);
}
AudioDiscardHelper::~AudioDiscardHelper() = default;
size_t AudioDiscardHelper::TimeDeltaToFrames(base::TimeDelta duration) const {
DCHECK(duration >= base::TimeDelta());
return duration.InSecondsF() * sample_rate_ + 0.5;
}
void AudioDiscardHelper::Reset(size_t initial_discard) {
discard_frames_ = initial_discard;
last_input_timestamp_ = kNoTimestamp;
timestamp_helper_.SetBaseTimestamp(kNoTimestamp);
delayed_discard_padding_ = DecoderBuffer::DiscardPadding();
}
bool AudioDiscardHelper::ProcessBuffers(
const DecoderBuffer::TimeInfo& time_info,
AudioBuffer* decoded_buffer) {
DCHECK(time_info.timestamp != kNoTimestamp);
// Issue a debug warning when we see non-monotonic timestamps. Only a warning
// to allow chained OGG playback.
WarnOnNonMonotonicTimestamps(last_input_timestamp_, time_info.timestamp);
last_input_timestamp_ = time_info.timestamp;
// If this is the first buffer seen, setup the timestamp helper.
if (!initialized()) {
// Clamp the base timestamp to zero.
timestamp_helper_.SetBaseTimestamp(
std::max(base::TimeDelta(), time_info.timestamp));
}
DCHECK(initialized());
if (!decoded_buffer) {
// If there's a one buffer delay for decoding, we need to save it so it can
// be processed with the next decoder buffer.
if (delayed_discard_)
delayed_discard_padding_ = time_info.discard_padding;
return false;
}
const size_t original_frame_count = decoded_buffer->frame_count();
// If there's a one buffer delay for decoding, pick up the last encoded
// buffer's discard padding for processing with the current decoded buffer.
DecoderBuffer::DiscardPadding current_discard_padding =
time_info.discard_padding;
if (delayed_discard_) {
// For simplicity disallow cases where decoder delay is present with delayed
// discard (no codecs at present). Doing so allows us to avoid complexity
// around endpoint tracking when handling complete buffer discards.
DCHECK_EQ(decoder_delay_, 0u);
std::swap(current_discard_padding, delayed_discard_padding_);
}
if (discard_frames_ > 0) {
const size_t decoded_frames = decoded_buffer->frame_count();
const size_t frames_to_discard = std::min(discard_frames_, decoded_frames);
discard_frames_ -= frames_to_discard;
DVLOG(1) << "Initial discard of " << frames_to_discard << " out of "
<< decoded_frames << " frames.";
// If everything would be discarded, indicate a new buffer is required.
if (frames_to_discard == decoded_frames) {
// For simplicity, we just drop any discard padding if |discard_frames_|
// consumes the entire buffer.
return false;
}
decoded_buffer->TrimStart(frames_to_discard);
}
// Process any delayed end discard from the previous buffer.
if (delayed_end_discard_ > 0) {
DCHECK_GT(decoder_delay_, 0u);
const size_t discard_index = decoder_delay_ - delayed_end_discard_;
DCHECK_LT(discard_index, decoder_delay_);
const size_t decoded_frames = decoded_buffer->frame_count();
DCHECK_LT(delayed_end_discard_, decoded_frames);
DVLOG(1) << "Delayed end discard of " << delayed_end_discard_ << " out of "
<< decoded_frames << " frames starting at " << discard_index;
decoded_buffer->TrimRange(discard_index,
discard_index + delayed_end_discard_);
delayed_end_discard_ = 0;
}
// Handle front discard padding.
if (current_discard_padding.first.is_positive()) {
const size_t decoded_frames = decoded_buffer->frame_count();
// If a complete buffer discard is requested and there's no decoder delay,
// just discard all remaining frames from this buffer. With decoder delay
// we have to estimate the correct number of frames to discard based on the
// duration of the encoded buffer.
const size_t start_frames_to_discard =
current_discard_padding.first == kInfiniteDuration
? (decoder_delay_ > 0 ? TimeDeltaToFrames(time_info.duration)
: decoded_frames)
: TimeDeltaToFrames(current_discard_padding.first);
// Regardless of the timestamp on the encoded buffer, the corresponding
// decoded output will appear |decoder_delay_| frames later.
size_t discard_start = decoder_delay_;
if (decoder_delay_ > 0) {
// If we have a |decoder_delay_| and have already discarded frames from
// this buffer, the |discard_start| must be adjusted by the number of
// frames already discarded.
const size_t frames_discarded_so_far =
original_frame_count - decoded_buffer->frame_count();
CHECK_LE(frames_discarded_so_far, decoder_delay_);
discard_start -= frames_discarded_so_far;
}
// For simplicity require the start of the discard to be within the current
// buffer. Doing so allows us avoid complexity around tracking discards
// across buffers.
if (discard_start >= decoded_frames) {
DLOG(ERROR)
<< "Unsupported discard padding and decoder delay mix. Due to "
"decoder delay, discard padding indicates data beyond the current "
"buffer should be discarded. This is not supported.";
return false;
}
const size_t frames_to_discard =
std::min(start_frames_to_discard, decoded_frames - discard_start);
// Carry over any frames which need to be discarded from the front of the
// next buffer.
DCHECK(!discard_frames_);
discard_frames_ = start_frames_to_discard - frames_to_discard;
DVLOG(1) << "Front discard of " << frames_to_discard << " out of "
<< decoded_frames << " frames starting at " << discard_start;
// If everything would be discarded, indicate a new buffer is required.
if (frames_to_discard == decoded_frames) {
// The buffer should not have been marked with end discard if the front
// discard removes everything, though incorrect or imprecise duration
// metadata, combined with various trimming operations, might still have
// end discard marked here. For simplicity, we do not carry over any such
// end discard for handling later.
return false;
}
decoded_buffer->TrimRange(discard_start, discard_start + frames_to_discard);
} else {
DCHECK(current_discard_padding.first.is_zero());
}
// Handle end discard padding.
if (current_discard_padding.second.is_positive()) {
const size_t decoded_frames = decoded_buffer->frame_count();
size_t end_frames_to_discard =
TimeDeltaToFrames(current_discard_padding.second);
if (decoder_delay_) {
// Delayed end discard only works if the decoder delay is less than a
// single buffer.
if (decoder_delay_ >= original_frame_count) {
DLOG(ERROR) << "Encountered invalid discard padding value.";
return false;
}
// If the discard is >= the decoder delay, trim everything we can off the
// end of this buffer and the rest from the start of the next.
if (end_frames_to_discard >= decoder_delay_) {
DCHECK(!discard_frames_);
discard_frames_ = decoder_delay_;
end_frames_to_discard -= decoder_delay_;
} else {
DCHECK(!delayed_end_discard_);
std::swap(delayed_end_discard_, end_frames_to_discard);
}
}
if (end_frames_to_discard > decoded_frames) {
DLOG(ERROR) << "Encountered invalid discard padding value.";
return false;
}
if (end_frames_to_discard > 0) {
DVLOG(1) << "End discard of " << end_frames_to_discard << " out of "
<< decoded_frames;
// If everything would be discarded, indicate a new buffer is required.
if (end_frames_to_discard == decoded_frames)
return false;
decoded_buffer->TrimEnd(end_frames_to_discard);
}
} else {
DCHECK(current_discard_padding.second.is_zero());
}
DVLOG(3) << __func__ << " ts: " << timestamp_helper_.GetTimestamp()
<< " frames: " << decoded_buffer->frame_count();
// Assign timestamp to the buffer.
decoded_buffer->set_timestamp(timestamp_helper_.GetTimestamp());
timestamp_helper_.AddFrames(decoded_buffer->frame_count());
return true;
}
} // namespace media