Problem handling MPEG-1 audio.

[Canta]

System info

Operating System: Ubuntu 20.04
Shaka Packager Version: f0a52cb

Issue and steps to reproduce the problem

The issue is simple: while trying to test the new DVBSUB functionality on a file I got from internet, shaka-packager fails.
@kqyang mentioned in #903 that this is a MPEG-1 audio handling problem, and should be dealt within a different ticket, so I create this one.

Here are the steps to reproduce the problem:

1. Download https://cs1.ssltrust.me/s/vR791a3ebbJio49 (workplace warning: subtitles contains adult language)
2. Run the packager command in the same dir the file was downloaded.

Packager Command:

/path/to/packager \
'in=file3.ts,stream=0,init_segment=1080p_init.mp4,segment_template=1080p_$Number$.m4s,playlist_name=1080p.m3u8' \
'in=file3.ts,stream=1,skip_encryption=1,init_segment=audio_init_0.mp4,segment_template=audio_0_$Number$.m4s,hls_name=POL,playlist_name=audio0.m3u8' \
'in=file3.ts,stream=2,skip_encryption=1,init_segment=audio_init_1.mp4,segment_template=audio_1_$Number$.m4s,hls_name=EN,playlist_name=audio1.m3u8' \
'in=file3.ts,stream=3,skip_encryption=1,format=ttml+mp4,init_segment=text_init.mp4,segment_template=text_$Number$.mp4,playlist_name=text.m3u8' \
--hls_master_playlist_output playlist.m3u8 \
--hls_playlist_type LIVE \
--default_language pol \
--default_text_language pol \
--time_shift_buffer_depth 60

What is the expected result?:
Some segments and playlists.

What happens instead?:

[0302/181526:INFO:demuxer.cc(89)] Demuxer::Run() on file 'file3.ts'.
[0302/181526:INFO:demuxer.cc(155)] Initialize Demuxer for file 'file3.ts'.
[0302/181526:FATAL:bit_writer.cc(18)] Check failed: bits < 1ULL << number_of_bits (33 vs. 32)
#0 0x0000004a07ee base::debug::StackTrace::StackTrace()
#1 0x00000044a4cf logging::LogMessage::~LogMessage()
#2 0x000000f9ea56 shaka::media::BitWriter::WriteBits()
#3 0x000000d72ee6 shaka::media::mp2t::Mpeg1Header::GetAudioSpecificConfig()
#4 0x000000d55d4a shaka::media::mp2t::EsParserAudio::UpdateAudioConfiguration()
#5 0x000000d5558f shaka::media::mp2t::EsParserAudio::Parse()
#6 0x000000d4c636 shaka::media::mp2t::TsSectionPes::ParseInternal()
#7 0x000000d4a433 shaka::media::mp2t::TsSectionPes::Emit()
#8 0x000000d4a261 shaka::media::mp2t::TsSectionPes::Parse()
#9 0x000000d32b35 shaka::media::mp2t::PidState::PushTsPacket()
#10 0x000000d3475b shaka::media::mp2t::Mp2tMediaParser::Parse()
#11 0x000000d23a78 shaka::media::Demuxer::InitializeParser()
#12 0x000000d22875 shaka::media::Demuxer::Run()
#13 0x000000682f1c shaka::media::Job::Run()
#14 0x000000586cd9 base::SimpleThread::ThreadMain()
#15 0x00000048660a base::(anonymous namespace)::ThreadFunc()
#16 0x7ff052cdb609 start_thread
#17 0x7ff052c02293 clone

Aborted (core dumped)

[kqyang]

@Canta Thanks for the bug report. Will you be interested in sending a PR to fix the bug?

The code at https://github.com/google/shaka-packager/blob/2909ca0c774dd9530ee188b1de499c7eef8e91d6/packager/media/formats/mp2t/mpeg1_header.cc#L199 is incorrect as the object type is more than 5 bits.

Here is the definition in the spec (ISO/IEC 14496:3 Table 1.16):

Syntax	No. of bits
audioObjectType;	5
if (audioObjectType == 31) {
audioObjectType = 32 + audioObjectTypeExt;	6
}

So we'll need to do:

// ISO/IEC 14496:3 Table 1.16 Syntax of GetAudioObjetType()
auto object_type = GetObjectType();
if (object_type <= 31) {
  config.WriteBits(object_type, 5); 
} else {
  config.WriteBits(31, 5); 
  config.WriteBits(object_type - 32, 6); 
}

[Canta]

I'll be happy to help. Yet, can't focus on this right now, as I have other pressing matters I need to solve first. Most likely will do this next week.