Example of verifying Dolby AC-4 specific boxes
You can use MP4drop to dump human-readable box information from an MP4 file and then verify that the boxes specific to Dolby AC-4 are set correctly for each of the Dolby AC-4 tracks in the MP4 file.
About this task
This test verifies the contents of the
/moov/trak[x]/mdia/minf/stbl/stsd/ac-4 box in a test stream,
where [x] is the track ID of the Dolby AC-4
track. For test cases that contain multiple Dolby AC-4 tracks
(multiple .mp4 files, correspondingly), you must run
MP4drop on each file that contains Dolby AC-4 data.
Procedure
- Locate the test stream Audio_ID_2ch_64kbps_25fps_ac4, and then copy it to the directory that contains MP4drop.
-
Run this command:
mp4drop Audio_ID_2ch_64kbps_25fps_ac4 -m 0 > test.xmllibrary_booksNote: For test cases containing multiple Dolby AC-4 tracks, run MP4drop on each of them and examine the results.The command generates this information in the test.xml file:<ftyp size="20"> <moov size="582"> <mvhd size="100"> <trak size="410"> <tkhd size="84"> <mdia size="310"> <mdhd size="24"> <hdlr size="38"> <minf size="217"> <smhd size="8"> <dinf size="28"> <stbl size="157"> <stsd size="81"> unsigned int(8) version = 0; unsigned int(24) flags = 0; unsigned int(32) entry_count = 1; <ac-4 size="65"> unsigned int(8) reserved = 0; unsigned int(8) reserved = 0; unsigned int(8) reserved = 0; unsigned int(8) reserved = 0; unsigned int(8) reserved = 0; unsigned int(8) reserved = 0; unsigned int(16) data_reference_index = 1; unsigned int(32) reserved = 0; unsigned int(32) reserved = 0; unsigned int(16) channelcount = 2; unsigned int(16) samplesize = 16; unsigned int(32) reserved = 0; unsigned int(16) samplerate = 48000; unsigned int(16) reserved = 0; <dac4 size="29"> unsigned int(3) ac4_dsi_version = 1; unsigned int(7) bitstream_version = 2; unsigned int(1) fs_index = 1; unsigned int(4) frame_rate_index = 2; unsigned int(9) n_presentations = 1; unsigned int(1) b_program_id = 0; unsigned int(2) bit_rate_mode = 2; unsigned int(32) bit_rate = 0; unsigned int(32) bit_rate_precision = 4294967295; unsigned int(5) byte_align = 0; unsigned int(8) presentation_version = 1; unsigned int(8) pres_bytes = 15; unsigned int(5) presentation_config_v1 = 31; unsigned int(3) mdcompat = 0; unsigned int(1) b_presentation_group_index = 1; unsigned int(5) presentation_group_index = 0; unsigned int(2) dsi_frame_rate_multiply_info = 0; unsigned int(2) dsi_frame_rate_fraction_info = 0; unsigned int(5) presentation_emdf_version = 0; unsigned int(10) presentation_key_id = 0; unsigned int(1) b_presentation_channel_coded = 1; unsigned int(5) dsi_presentation_ch_mode = 1; unsigned int(24) presentation_channel_mask_v1 = 1; unsigned int(1) b_presentation_core_differs = 0; unsigned int(1) b_presentation_filter = 0; unsigned int(1) b_substreams_present = 1; unsigned int(1) b_hsf_ext = 0; unsigned int(1) b_channel_coded = 1; unsigned int(8) n_substreams = 1; unsigned int(2) dsi_sf_multiplier = 0; unsigned int(1) b_substream_bitrate_indicator = 0; unsigned int(24) dsi_substream_channel_mask = 1; unsigned int(1) b_content_type = 1; unsigned int(3) content_classifier = 0; unsigned int(1) b_language_indicator = 0; unsigned int(1) b_pre_virtualized = 0; unsigned int(1) b_add_emdf_substreams = 0; unsigned int(1) b_presentation_bitrate_info = 0; unsigned int(1) b_alternative = 0; unsigned int(1) de_indicator = 1; unsigned int(1) dolby_atmos_indicator = 0; unsigned int(4) reserved = 0; unsigned int(1) b_extended_presentation_id = 0; unsigned int(1) reserved = 0; </dac4> </ac-4> -
Examine the generated XML file in an XML editor, and verify that the
ac-4anddac4box information written to the XML file contains the values specified in the expected results.