representation.cc

// Copyright 2017 Google LLC. All rights reserved.
//
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file or at
// https://developers.google.com/open-source/licenses/bsd
 
#include <packager/mpd/base/representation.h>
 
#include <algorithm>
#include <cstdint>
#include <cstdlib>
#include <list>
#include <memory>
#include <optional>
#include <string>
#include <utility>
 
#include <absl/log/check.h>
#include <absl/log/log.h>
#include <absl/strings/str_format.h>
 
#include <packager/file.h>
#include <packager/media/base/muxer_util.h>
#include <packager/mpd/base/media_info.pb.h>
#include <packager/mpd/base/mpd_options.h>
#include <packager/mpd/base/mpd_utils.h>
#include <packager/mpd/base/xml/xml_node.h>
 
namespace shaka {
namespace {
 
std::string GetMimeType(const std::string& prefix,
                        MediaInfo::ContainerType container_type) {
  switch (container_type) {
    case MediaInfo::CONTAINER_MP4:
      return prefix + "/mp4";
    case MediaInfo::CONTAINER_MPEG2_TS:
      // NOTE: DASH MPD spec uses lowercase but RFC3555 says uppercase.
      return prefix + "/MP2T";
    case MediaInfo::CONTAINER_WEBM:
      return prefix + "/webm";
    default:
      break;
  }
 
  // Unsupported container types should be rejected/handled by the caller.
  LOG(ERROR) << "Unrecognized container type: " << container_type;
  return std::string();
}
 
// Check whether the video info has width and height.
// DASH IOP also requires several other fields for video representations, namely
// width, height, framerate, and sar.
bool HasRequiredVideoFields(const MediaInfo_VideoInfo& video_info) {
  if (!video_info.has_height() || !video_info.has_width()) {
    LOG(ERROR)
        << "Width and height are required fields for generating a valid MPD.";
    return false;
  }
  // These fields are not required for a valid MPD, but required for DASH IOP
  // compliant MPD. MpdBuilder can keep generating MPDs without these fields.
  LOG_IF(WARNING, !video_info.has_time_scale())
      << "Video info does not contain timescale required for "
         "calculating framerate. @frameRate is required for DASH IOP.";
  LOG_IF(WARNING, !video_info.has_pixel_width())
      << "Video info does not contain pixel_width to calculate the sample "
         "aspect ratio required for DASH IOP.";
  LOG_IF(WARNING, !video_info.has_pixel_height())
      << "Video info does not contain pixel_height to calculate the sample "
         "aspect ratio required for DASH IOP.";
  return true;
}
 
int32_t GetTimeScale(const MediaInfo& media_info) {
  if (media_info.has_reference_time_scale()) {
    return media_info.reference_time_scale();
  }
 
  if (media_info.has_video_info()) {
    return media_info.video_info().time_scale();
  }
 
  if (media_info.has_audio_info()) {
    return media_info.audio_info().time_scale();
  }
 
  LOG(WARNING) << "No timescale specified, using 1 as timescale.";
  return 1;
}
 
}  // namespace
 
Representation::Representation(
    const MediaInfo& media_info,
    const MpdOptions& mpd_options,
    uint32_t id,
    std::unique_ptr<RepresentationStateChangeListener> state_change_listener)
    : media_info_(media_info),
      id_(id),
      mpd_options_(mpd_options),
      state_change_listener_(std::move(state_change_listener)),
      allow_approximate_segment_timeline_(
          // TODO(kqyang): Need a better check. $Time is legitimate but not a
          // template.
          media_info.segment_template().find("$Time") == std::string::npos &&
          mpd_options_.mpd_params.allow_approximate_segment_timeline) {}
 
Representation::Representation(
    const Representation& representation,
    std::unique_ptr<RepresentationStateChangeListener> state_change_listener)
    : Representation(representation.media_info_,
                     representation.mpd_options_,
                     representation.id_,
                     std::move(state_change_listener)) {
  mime_type_ = representation.mime_type_;
  codecs_ = representation.codecs_;
}
 
Representation::~Representation() {}
 
bool Representation::Init() {
  if (!AtLeastOneTrue(media_info_.has_video_info(),
                      media_info_.has_audio_info(),
                      media_info_.has_text_info())) {
    // This is an error. Segment information can be in AdaptationSet, Period, or
    // MPD but the interface does not provide a way to set them.
    // See 5.3.9.1 ISO 23009-1:2012 for segment info.
    LOG(ERROR) << "Representation needs one of video, audio, or text.";
    return false;
  }
 
  if (MoreThanOneTrue(media_info_.has_video_info(),
                      media_info_.has_audio_info(),
                      media_info_.has_text_info())) {
    LOG(ERROR) << "Only one of VideoInfo, AudioInfo, or TextInfo can be set.";
    return false;
  }
 
  if (media_info_.container_type() == MediaInfo::CONTAINER_UNKNOWN) {
    LOG(ERROR) << "'container_type' in MediaInfo cannot be CONTAINER_UNKNOWN.";
    return false;
  }
 
  if (media_info_.has_video_info()) {
    mime_type_ = GetVideoMimeType();
    if (!HasRequiredVideoFields(media_info_.video_info())) {
      LOG(ERROR) << "Missing required fields to create a video Representation.";
      return false;
    }
  } else if (media_info_.has_audio_info()) {
    mime_type_ = GetAudioMimeType();
  } else if (media_info_.has_text_info()) {
    mime_type_ = GetTextMimeType();
  }
 
  if (mime_type_.empty())
    return false;
 
  codecs_ = GetCodecs(media_info_);
  supplemental_codecs_ = GetSupplementalCodecs(media_info_);
  supplemental_profiles_ = GetSupplementalProfiles(media_info_);
  return true;
}
 
void Representation::AddContentProtectionElement(
    const ContentProtectionElement& content_protection_element) {
  content_protection_elements_.push_back(content_protection_element);
  RemoveDuplicateAttributes(&content_protection_elements_.back());
}
 
void Representation::UpdateContentProtectionPssh(const std::string& drm_uuid,
                                                 const std::string& pssh) {
  UpdateContentProtectionPsshHelper(drm_uuid, pssh,
                                    &content_protection_elements_);
}
 
void Representation::AddNewSegment(int64_t start_time,
                                   int64_t duration,
                                   uint64_t size,
                                   int64_t segment_number) {
  if (start_time == 0 && duration == 0) {
    LOG(WARNING) << "Got segment with start_time and duration == 0. Ignoring.";
    return;
  }
 
  // In order for the oldest segment to be accessible for at least
  // |time_shift_buffer_depth| seconds, the latest segment should not be in the
  // sliding window since the player could be playing any part of the latest
  // segment. So the current segment duration is added to the sum of segment
  // durations (in the manifest/playlist) after sliding the window.
  SlideWindow();
 
  if (state_change_listener_)
    state_change_listener_->OnNewSegmentForRepresentation(start_time, duration);
 
  AddSegmentInfo(start_time, duration, segment_number);
 
  // Only update the buffer depth and bandwidth estimator when the full segment
  // is completed. In the low latency case, only the first chunk in the segment
  // has been written at this point. Therefore, we must wait until the entire
  // segment has been written before updating buffer depth and bandwidth
  // estimator.
  if (!mpd_options_.mpd_params.low_latency_dash_mode) {
    current_buffer_depth_ += segment_infos_.back().duration;
 
    bandwidth_estimator_.AddBlock(size, static_cast<double>(duration) /
                                            media_info_.reference_time_scale());
  }
}
 
void Representation::UpdateCompletedSegment(int64_t duration, uint64_t size) {
  if (!mpd_options_.mpd_params.low_latency_dash_mode) {
    LOG(WARNING)
        << "UpdateCompletedSegment is only applicable to low latency mode.";
    return;
  }
 
  UpdateSegmentInfo(duration);
 
  current_buffer_depth_ += segment_infos_.back().duration;
 
  bandwidth_estimator_.AddBlock(
      size, static_cast<double>(duration) / media_info_.reference_time_scale());
}
 
void Representation::SetSampleDuration(int32_t frame_duration) {
  // Sample duration is used to generate approximate SegmentTimeline.
  // Text is required to have exactly the same segment duration.
  if (media_info_.has_audio_info() || media_info_.has_video_info())
    frame_duration_ = frame_duration;
 
  if (media_info_.has_video_info()) {
    media_info_.mutable_video_info()->set_frame_duration(frame_duration);
    if (state_change_listener_) {
      state_change_listener_->OnSetFrameRateForRepresentation(
          frame_duration, media_info_.video_info().time_scale());
    }
  }
}
 
void Representation::SetSegmentDuration() {
  int64_t sd = mpd_options_.mpd_params.target_segment_duration *
               media_info_.reference_time_scale();
  if (sd <= 0)
    return;
  media_info_.set_segment_duration(sd);
}
 
const MediaInfo& Representation::GetMediaInfo() const {
  return media_info_;
}
 
// Uses info in |media_info_| and |content_protection_elements_| to create a
// "Representation" node.
// MPD schema has strict ordering. The following must be done in order.
// AddVideoInfo() (possibly adds FramePacking elements), AddAudioInfo() (Adds
// AudioChannelConfig elements), AddContentProtectionElements*(), and
// AddVODOnlyInfo() (Adds segment info).
std::optional<xml::XmlNode> Representation::GetXml() {
  if (!HasRequiredMediaInfoFields()) {
    LOG(ERROR) << "MediaInfo missing required fields.";
    return std::nullopt;
  }
 
  const uint64_t bandwidth = media_info_.has_bandwidth()
                                 ? media_info_.bandwidth()
                                 : bandwidth_estimator_.Max();
 
  DCHECK(!(HasVODOnlyFields(media_info_) && HasLiveOnlyFields(media_info_)));
 
  xml::RepresentationXmlNode representation;
  // Mandatory fields for Representation.
  if (!representation.SetId(id_) ||
      !representation.SetIntegerAttribute("bandwidth", bandwidth) ||
      !(codecs_.empty() ||
        representation.SetStringAttribute("codecs", codecs_)) ||
      !representation.SetStringAttribute("mimeType", mime_type_)) {
    return std::nullopt;
  }
 
  if (!supplemental_codecs_.empty() && !supplemental_profiles_.empty()) {
    if (!representation.SetStringAttribute("scte214:supplementalCodecs",
                                           supplemental_codecs_) ||
        !representation.SetStringAttribute("scte214:supplementalProfiles",
                                           supplemental_profiles_)) {
      LOG(ERROR) << "Failed to add supplemental codecs/profiles to "
                    "Representation XML.";
    }
  }
 
  const bool has_video_info = media_info_.has_video_info();
  const bool has_audio_info = media_info_.has_audio_info();
 
  if (has_video_info &&
      !representation.AddVideoInfo(
          media_info_.video_info(),
          !(output_suppression_flags_ & kSuppressWidth),
          !(output_suppression_flags_ & kSuppressHeight),
          !(output_suppression_flags_ & kSuppressFrameRate))) {
    LOG(ERROR) << "Failed to add video info to Representation XML.";
    return std::nullopt;
  }
 
  if (has_audio_info &&
      !representation.AddAudioInfo(media_info_.audio_info())) {
    LOG(ERROR) << "Failed to add audio info to Representation XML.";
    return std::nullopt;
  }
 
  if (!representation.AddContentProtectionElements(
          content_protection_elements_)) {
    return std::nullopt;
  }
 
  if (HasVODOnlyFields(media_info_) &&
      !representation.AddVODOnlyInfo(
          media_info_, mpd_options_.mpd_params.use_segment_list,
          mpd_options_.mpd_params.target_segment_duration)) {
    LOG(ERROR) << "Failed to add VOD info.";
    return std::nullopt;
  }
 
  if (HasLiveOnlyFields(media_info_) &&
      !representation.AddLiveOnlyInfo(
          media_info_, segment_infos_,
          mpd_options_.mpd_params.low_latency_dash_mode)) {
    LOG(ERROR) << "Failed to add Live info.";
    return std::nullopt;
  }
  // TODO(rkuroiwa): It is likely that all representations have the exact same
  // SegmentTemplate. Optimize and propagate the tag up to AdaptationSet level.
 
  output_suppression_flags_ = 0;
  return representation;
}
 
void Representation::SuppressOnce(SuppressFlag flag) {
  output_suppression_flags_ |= flag;
}
 
void Representation::SetPresentationTimeOffset(
    double presentation_time_offset) {
  int64_t pto = presentation_time_offset * media_info_.reference_time_scale();
  if (pto <= 0)
    return;
  media_info_.set_presentation_time_offset(pto);
}
 
void Representation::SetAvailabilityTimeOffset() {
  // Adjust the frame duration to units of seconds to match target segment
  // duration.
  const double frame_duration_sec =
      (double)frame_duration_ / (double)media_info_.reference_time_scale();
  // availabilityTimeOffset = segment duration - chunk duration.
  // Here, the frame duration is equivalent to the sample duration,
  // see Representation::SetSampleDuration(uint32_t frame_duration).
  // By definition, each chunk will contain only one sample;
  // thus, chunk_duration = sample_duration = frame_duration.
  const double ato =
      mpd_options_.mpd_params.target_segment_duration - frame_duration_sec;
  if (ato <= 0)
    return;
  media_info_.set_availability_time_offset(ato);
}
 
bool Representation::GetStartAndEndTimestamps(
    double* start_timestamp_seconds,
    double* end_timestamp_seconds) const {
  if (segment_infos_.empty())
    return false;
 
  if (start_timestamp_seconds) {
    *start_timestamp_seconds =
        static_cast<double>(segment_infos_.begin()->start_time) /
        GetTimeScale(media_info_);
  }
  if (end_timestamp_seconds) {
    *end_timestamp_seconds =
        static_cast<double>(segment_infos_.rbegin()->start_time +
                            segment_infos_.rbegin()->duration *
                                (segment_infos_.rbegin()->repeat + 1)) /
        GetTimeScale(media_info_);
  }
  return true;
}
 
bool Representation::HasRequiredMediaInfoFields() const {
  if (HasVODOnlyFields(media_info_) && HasLiveOnlyFields(media_info_)) {
    LOG(ERROR) << "MediaInfo cannot have both VOD and Live fields.";
    return false;
  }
 
  if (!media_info_.has_container_type()) {
    LOG(ERROR) << "MediaInfo missing required field: container_type.";
    return false;
  }
 
  return true;
}
 
void Representation::AddSegmentInfo(int64_t start_time,
                                    int64_t duration,
                                    int64_t segment_number) {
  const uint64_t kNoRepeat = 0;
  const int64_t adjusted_duration = AdjustDuration(duration);
 
  if (!segment_infos_.empty()) {
    // Contiguous segment.
    const SegmentInfo& previous = segment_infos_.back();
    const int64_t previous_segment_end_time =
        previous.start_time + previous.duration * (previous.repeat + 1);
    // Make it continuous if the segment start time is close to previous segment
    // end time.
    if (ApproximiatelyEqual(previous_segment_end_time, start_time)) {
      const int64_t segment_end_time_for_same_duration =
          previous_segment_end_time + previous.duration;
      const int64_t actual_segment_end_time = start_time + duration;
      // Consider the segments having identical duration if the segment end time
      // is close to calculated segment end time by assuming identical duration.
      if (ApproximiatelyEqual(segment_end_time_for_same_duration,
                              actual_segment_end_time)) {
        ++segment_infos_.back().repeat;
      } else {
        segment_infos_.push_back(
            {previous_segment_end_time,
             actual_segment_end_time - previous_segment_end_time, kNoRepeat,
             segment_number});
      }
      return;
    }
 
    // A gap since previous.
    const int64_t kRoundingErrorGrace = 5;
    if (previous_segment_end_time + kRoundingErrorGrace < start_time) {
      LOG(WARNING) << RepresentationAsString() << " Found a gap of size "
                   << (start_time - previous_segment_end_time)
                   << " > kRoundingErrorGrace (" << kRoundingErrorGrace
                   << "). The new segment starts at " << start_time
                   << " but the previous segment ends at "
                   << previous_segment_end_time << ".";
    }
 
    // No overlapping segments.
    if (start_time < previous_segment_end_time - kRoundingErrorGrace) {
      LOG(WARNING)
          << RepresentationAsString()
          << " Segments should not be overlapping. The new segment starts at "
          << start_time << " but the previous segment ends at "
          << previous_segment_end_time << ".";
    }
  }
  segment_infos_.push_back(
      {start_time, adjusted_duration, kNoRepeat, segment_number});
}
 
void Representation::UpdateSegmentInfo(int64_t duration) {
  if (!segment_infos_.empty()) {
    // Update the duration in the current segment.
    segment_infos_.back().duration = duration;
  }
}
 
bool Representation::ApproximiatelyEqual(int64_t time1, int64_t time2) const {
  if (!allow_approximate_segment_timeline_)
    return time1 == time2;
 
  // It is not always possible to align segment duration to target duration
  // exactly. For example, for AAC with sampling rate of 44100, there are always
  // 1024 audio samples per frame, so the frame duration is 1024/44100. For a
  // target duration of 2 seconds, the closest segment duration would be 1.984
  // or 2.00533.
 
  // An arbitrary error threshold cap. This makes sure that the error is not too
  // large for large samples.
  const double kErrorThresholdSeconds = 0.05;
 
  // So we consider two times equal if they differ by less than one sample.
  const int32_t error_threshold =
      std::min(frame_duration_,
               static_cast<int32_t>(kErrorThresholdSeconds *
                                    media_info_.reference_time_scale()));
  return std::abs(time1 - time2) <= error_threshold;
}
 
int64_t Representation::AdjustDuration(int64_t duration) const {
  if (!allow_approximate_segment_timeline_)
    return duration;
  const int64_t scaled_target_duration =
      mpd_options_.mpd_params.target_segment_duration *
      media_info_.reference_time_scale();
  return ApproximiatelyEqual(scaled_target_duration, duration)
             ? scaled_target_duration
             : duration;
}
 
void Representation::SlideWindow() {
  if (mpd_options_.mpd_params.time_shift_buffer_depth <= 0.0 ||
      mpd_options_.mpd_type == MpdType::kStatic)
    return;
 
  const int32_t time_scale = GetTimeScale(media_info_);
  DCHECK_GT(time_scale, 0);
 
  const int64_t time_shift_buffer_depth = static_cast<int64_t>(
      mpd_options_.mpd_params.time_shift_buffer_depth * time_scale);
 
  if (current_buffer_depth_ <= time_shift_buffer_depth)
    return;
 
  std::list<SegmentInfo>::iterator first = segment_infos_.begin();
  std::list<SegmentInfo>::iterator last = first;
  for (; last != segment_infos_.end(); ++last) {
    // Remove the current segment only if it falls completely out of time shift
    // buffer range.
    while (last->repeat >= 0 &&
           current_buffer_depth_ - last->duration >= time_shift_buffer_depth) {
      current_buffer_depth_ -= last->duration;
      RemoveOldSegment(&*last);
    }
    if (last->repeat >= 0)
      break;
  }
  segment_infos_.erase(first, last);
}
 
void Representation::RemoveOldSegment(SegmentInfo* segment_info) {
  int64_t segment_start_time = segment_info->start_time;
  segment_info->start_time += segment_info->duration;
  segment_info->repeat--;
  int64_t start_number = segment_info->start_segment_number;
  segment_info->start_segment_number++;
 
  if (mpd_options_.mpd_params.preserved_segments_outside_live_window == 0)
    return;
 
  segments_to_be_removed_.push_back(
      media::GetSegmentName(media_info_.segment_template(), segment_start_time,
                            start_number, media_info_.bandwidth()));
  while (segments_to_be_removed_.size() >
         mpd_options_.mpd_params.preserved_segments_outside_live_window) {
    const std::string& file_name = segments_to_be_removed_.front();
    VLOG(2) << "Deleting " << file_name;
    // DASH and HLS outputs could both be tracking the same files and are in a
    // race to delete them. Delete() returns false if the file does not exist,
    // but we only want to retry if the file does exist (indicating a failure
    // to delete, rather than the file already being gone). GetFileSize()
    // returns >= 0 if the file exists, and < 0 if it does not.
    if (!File::Delete(file_name.c_str()) &&
        File::GetFileSize(file_name.c_str()) >= 0) {
      LOG(WARNING) << "Failed to delete " << file_name << "; Will retry later.";
      break;
    }
    segments_to_be_removed_.pop_front();
  }
}
 
std::string Representation::GetVideoMimeType() const {
  return GetMimeType("video", media_info_.container_type());
}
 
std::string Representation::GetAudioMimeType() const {
  return GetMimeType("audio", media_info_.container_type());
}
 
std::string Representation::GetTextMimeType() const {
  CHECK(media_info_.has_text_info());
  if (media_info_.text_info().codec() == "ttml") {
    switch (media_info_.container_type()) {
      case MediaInfo::CONTAINER_TEXT:
        return "application/ttml+xml";
      case MediaInfo::CONTAINER_MP4:
        return "application/mp4";
      default:
        LOG(ERROR) << "Failed to determine MIME type for TTML container: "
                   << media_info_.container_type();
        return "";
    }
  }
  if (media_info_.text_info().codec() == "wvtt") {
    if (media_info_.container_type() == MediaInfo::CONTAINER_TEXT) {
      return "text/vtt";
    } else if (media_info_.container_type() == MediaInfo::CONTAINER_MP4) {
      return "application/mp4";
    }
    LOG(ERROR) << "Failed to determine MIME type for VTT container: "
               << media_info_.container_type();
    return "";
  }
 
  LOG(ERROR) << "Cannot determine MIME type for format: "
             << media_info_.text_info().codec()
             << " container: " << media_info_.container_type();
  return "";
}
 
std::string Representation::RepresentationAsString() const {
  std::string s = absl::StrFormat("Representation (id=%d,", id_);
  if (media_info_.has_video_info()) {
    const MediaInfo_VideoInfo& video_info = media_info_.video_info();
    absl::StrAppendFormat(&s, "codec='%s',width=%d,height=%d",
                          video_info.codec().c_str(), video_info.width(),
                          video_info.height());
  } else if (media_info_.has_audio_info()) {
    const MediaInfo_AudioInfo& audio_info = media_info_.audio_info();
    absl::StrAppendFormat(
        &s, "codec='%s',frequency=%d,language='%s'", audio_info.codec().c_str(),
        audio_info.sampling_frequency(), audio_info.language().c_str());
  } else if (media_info_.has_text_info()) {
    const MediaInfo_TextInfo& text_info = media_info_.text_info();
    absl::StrAppendFormat(&s, "codec='%s',language='%s'",
                          text_info.codec().c_str(),
                          text_info.language().c_str());
  }
  absl::StrAppendFormat(&s, ")");
  return s;
}
 
}  // namespace shaka