Module: Robocap::SDK::Mp4Cenc

Defined in:
lib/robocap/sdk/mp4_cenc.rb

Constant Summary collapse

CEKA_TAG = 
'cenc_cek_wrapped_b64'
CUSTOMER_ID_TAG = 
'cenc_customer_id'
CUSTOMER_ID_FALLBACK_TAG = 
'username'
KID_TAG = 
'cenc_kid_hex'
CENC_WRAPPED_ALGO_TAG = 
'cenc_wrapped_algo'
CENC_STRIP_TAGS_ON_DECRYPT = 
[
  CEKA_TAG,
  CENC_WRAPPED_ALGO_TAG,
].freeze

Class Method Summary collapse

Class Method Details

.has_cenc_tags(mp4_path, ffprobe_executable: nil) ⇒ Object 



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# File 'lib/robocap/sdk/mp4_cenc.rb', line 105

def has_cenc_tags(mp4_path, ffprobe_executable: nil)
  tags = read_format_tags(mp4_path, ffprobe_executable: ffprobe_executable)
  return false unless tags[CEKA_TAG] && !tags[CEKA_TAG].empty?
  has_customer_id_source?(tags)
rescue Error
  false
end

.load_cenc_metadata(mp4_path, ffprobe_executable: nil) ⇒ Object 



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# File 'lib/robocap/sdk/mp4_cenc.rb', line 99

def load_cenc_metadata(mp4_path, ffprobe_executable: nil)
  parse_cenc_metadata_from_tags(
    read_format_tags(mp4_path, ffprobe_executable: ffprobe_executable),
  )
end

.parse_cenc_metadata_from_tags(tags) ⇒ Object 



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# File 'lib/robocap/sdk/mp4_cenc.rb', line 66

def parse_cenc_metadata_from_tags(tags)
  unless tags[CEKA_TAG] && !tags[CEKA_TAG].empty?
    raise Error.new(
      code: ErrorCode::ERR_CENC_TAGS_MISSING,
      message: "Missing CENC tags: #{CEKA_TAG}",
    )
  end

  customer_id = resolve_customer_id(tags)

  begin
    cek_wrapped = Base64.strict_decode64(tags[CEKA_TAG])
  rescue ArgumentError
    raise Error.new(
      code: ErrorCode::ERR_CENC_TAGS_MISSING,
      message: 'Invalid cenc_cek_wrapped_b64 Base64',
    )
  end

  unless cek_wrapped.bytesize == Config::RSA_2048_CIPHERTEXT_BYTES
    raise Error.new(
      code: ErrorCode::ERR_CENC_CEKA_WRAP,
      message: "Wrapped CEK must be #{Config::RSA_2048_CIPHERTEXT_BYTES} bytes",
    )
  end

  kid = tags[KID_TAG]
  kid = kid.strip.downcase if kid
  kid = nil if kid && kid.empty?

  CencMp4Metadata.new(customer_id: customer_id, cek_wrapped: cek_wrapped, kid_hex: kid)
end

.read_format_tags(mp4_path, ffprobe_executable: nil) ⇒ Object 



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# File 'lib/robocap/sdk/mp4_cenc.rb', line 29

def read_format_tags(mp4_path, ffprobe_executable: nil)
  path = Pathname(mp4_path).expand_path
  unless path.file?
    raise Error.new(
      code: ErrorCode::ERR_CENC_TAGS_MISSING,
      message: "MP4 file not found: #{path}",
    )
  end
  exe = FfmpegCli.resolve_ffprobe_executable(ffprobe_executable)
  stdout, stderr, status = FfmpegCli.open3_capture3(
    exe, '-v', 'error', '-show_format', '-print_format', 'json', path.to_s,
  )
  unless status.exitstatus.zero?
    raise Error.new(
      code: ErrorCode::ERR_CENC_FFPROBE_FAILED,
      message: "ffprobe failed: #{stderr}",
    )
  end

  payload = parse_ffprobe_json(stdout)
  fmt = payload['format']
  unless fmt.is_a?(Hash)
    raise Error.new(
      code: ErrorCode::ERR_CENC_TAGS_MISSING,
      message: 'ffprobe output missing format section',
    )
  end
  tags = fmt['tags']
  unless tags.is_a?(Hash)
    raise Error.new(
      code: ErrorCode::ERR_CENC_TAGS_MISSING,
      message: 'MP4 has no format metadata tags',
    )
  end
  tags.transform_keys(&:to_s).transform_values(&:to_s)
end