Shaka wrongly parses pts and dts values from mpegts stream after ffmpeg

[acris5]

System info

Operating System: docker
Shaka Packager Version: b5c2cb8

Issue and steps to reproduce the problem

I got http mpegts stream and decode it with ffmpeg and then pass to packager.
ffmpeg -re -i http://172.17.0.1:8008/2222 -map "0:v:0" -map "0:a:0" -map "0:s?" -map "0:d?" -forced-idr 1 -force_key_frames "expr:gte(t,n_forced*2)" -sc_threshold 0 -c:v:0 libx264 -c:a aac -c:s copy -copyts -f mpegts pipe: >/tmp/pipes/pipe1

packager
'in=/shaka-packager/pipes/pipe1,stream=video,init_segment=/shaka-results/bitrate_1/video_init.mp4,segment_template=/shaka-results/bitrate_1/video_$Number$.m4s,playlist_name=/shaka-results/bitrate_1/video.m3u8'
'in=/shaka-packager/pipes/pipe1,stream=audio,lang=ru,init_segment=/shaka-results/bitrate_1/audio_init.mp4,segment_template=/shaka-results/bitrate_1/audio_$Number$.m4s,playlist_name=/shaka-results/bitrate_1/audio.m3u8'
'in=/shaka-packager/pipes/pipe1,stream=text,format=ttml+mp4,init_segment=/shaka-results/bitrate_1/text_init.mp4,segment_template=/shaka-results/bitrate_1/text_$Number$.m4s,lang=ru,playlist_name=/shaka-results/bitrate_1/text.m3u8'
--max_hd_pixels 8294400 --hls_master_playlist_output /shaka-results/demo_master.m3u8 --mpd_output /shaka-results/manifest.mpd --hls_playlist_type LIVE
--segment_duration 2 --min_buffer_time 4 --suggested_presentation_delay 10 --time_shift_buffer_depth 12 --allow_approximate_segment_timeline --preserved_segments_outside_live_window 20

What is the expected result?
HLS and Dash output should contain video audio and teletext, but sometime it lacks some streams.

I noticed that it wrongly parses pts and dts and gets following different values:

2024-08-27T06:35:26.928729959Z TS Packet size=139 pts=-4160261398 dts=-9223372036854775808 data_alignment_indicator=1
2024-08-27T06:35:26.928733417Z TS Packet size=10866 pts=4429674000 dts=4429670400 data_alignment_indicator=0
2024-08-27T06:35:26.928736669Z TS Packet size=2695 pts=4429659343 dts=-9223372036854775808 data_alignment_indicator=0
2024-08-27T06:35:26.928740049Z TS Packet size=139 pts=-4160258691 dts=-9223372036854775808 data_alignment_indicator=1
2024-08-27T06:35:26.928743360Z TS Packet size=31525 pts=4429692000 dts=4429674000 data_alignment_indicator=0
2024-08-27T06:35:27.071983621Z TS Packet size=18825 pts=4429684800 dts=4429677600 data_alignment_indicator=0
2024-08-27T06:35:27.072142371Z TS Packet size=18 pts=126000 dts=-9223372036854775808 data_alignment_indicator=1
2024-08-27T06:35:27.072172674Z TS Packet size=18 pts=126000 dts=-9223372036854775808 data_alignment_indicator=1
2024-08-27T06:35:27.072190385Z TS Packet size=139 pts=-4160253277 dts=-9223372036854775808 data_alignment_indicator=1
2024-08-27T06:35:27.072205791Z TS Packet size=139 pts=-4160250569 dts=-9223372036854775808 data_alignment_indicator=1
2024-08-27T06:35:27.072216067Z TS Packet size=10122 pts=4429681200 dts=-9223372036854775808 data_alignment_indicator=0
2024-08-27T06:35:27.072322665Z TS Packet size=2910 pts=4429674703 dts=-9223372036854775808 data_alignment_indicator=0
2024-08-27T06:35:27.072339553Z TS Packet size=139 pts=-4160247862 dts=-9223372036854775808 data_alignment_indicator=1
2024-08-27T06:35:27.072345231Z TS Packet size=13549 pts=4429688400 dts=4429684800 data_alignment_indicator=0
2024-08-27T06:35:27.214525312Z TS Packet size=43954 pts=4429706400 dts=4429688400 data_alignment_indicator=0

While ffprobe shows that there are normal values instead:

ffprobe -v 0 -show_entries packet=pts,dts,size,codec_type  demo/pipes/pipe1 

[PACKET]
codec_type=subtitle
pts=4449578454
dts=4449578454
size=139
[SIDE_DATA]
[/SIDE_DATA]
[/PACKET]
[PACKET]
codec_type=subtitle
pts=4449578454
dts=4449578454
size=139
[SIDE_DATA]
[/SIDE_DATA]
[/PACKET]
[PACKET]
codec_type=video
pts=4449636000
dts=4449628800
size=22721
[SIDE_DATA]
[/SIDE_DATA]
[/PACKET]
[PACKET]
codec_type=subtitle
pts=4449600054
dts=4449600054
size=139
[SIDE_DATA]
[/SIDE_DATA]
[/PACKET]
[PACKET]
codec_type=subtitle
pts=4449600054
dts=4449600054
size=139
[SIDE_DATA]
[/SIDE_DATA]
[/PACKET]
[PACKET]
codec_type=video
pts=4449632400
dts=4449632400
size=15829
[SIDE_DATA]
[/SIDE_DATA]
[/PACKET]
[PACKET]
codec_type=data
pts=126000
dts=126000
size=18
[SIDE_DATA]

[acris5]

As I learned problem is somewhere in the following function

// Given that |time| is coded using 33 bits,
// UnrollTimestamp returns the corresponding unrolled timestamp.
// The unrolled timestamp is defined by:
// |time| + k * (2 ^ 33)
// where k is estimated so that the unrolled timestamp
// is as close as possible to |previous_unrolled_time|.
static int64_t UnrollTimestamp(int64_t previous_unrolled_time, int64_t time) {
  // Mpeg2 TS timestamps have an accuracy of 33 bits.
  const int nbits = 33;

  // |timestamp| has a precision of |nbits|
  // so make sure the highest bits are set to 0.
  DCHECK_EQ((time >> nbits), 0);

  // Consider 3 possibilities to estimate the missing high bits of |time|.
  int64_t previous_unrolled_time_high = (previous_unrolled_time >> nbits);
  int64_t time0 = ((previous_unrolled_time_high - 1) << nbits) | time;
  int64_t time1 = ((previous_unrolled_time_high + 0) << nbits) | time;
  int64_t time2 = ((previous_unrolled_time_high + 1) << nbits) | time;

  // Select the min absolute difference with the current time
  // so as to ensure time continuity.
  int64_t diff0 = time0 - previous_unrolled_time;
  int64_t diff1 = time1 - previous_unrolled_time;
  int64_t diff2 = time2 - previous_unrolled_time;
  if (diff0 < 0)
    diff0 = -diff0;
  if (diff1 < 0)
    diff1 = -diff1;
  if (diff2 < 0)
    diff2 = -diff2;

  int64_t unrolled_time;
  int64_t min_diff;
  if (diff1 < diff0) {
    unrolled_time = time1;
    min_diff = diff1;
  } else {
    unrolled_time = time0;
    min_diff = diff0;
  }
  if (diff2 < min_diff)
    unrolled_time = time2;
  std::cout<<"time: "<<time<<", unrolled: "<<unrolled_time<<std::endl;
  return unrolled_time;

2024-08-27T09:20:12.087333044Z time: 5319075769, unrolled: -3270858823
2024-08-27T09:20:12.087336357Z TS Packet size=139 pts=-3270858823 dts=-9223372036854775808 data_alignment_indicator=1
2024-08-27T09:20:12.087337907Z time: 5319078476, unrolled: -3270856116
2024-08-27T09:20:12.087339549Z TS Packet size=139 pts=-3270856116 dts=-9223372036854775808 data_alignment_indicator=1
2024-08-27T09:20:12.087341980Z time: 5319063823, unrolled: 5319063823
2024-08-27T09:20:12.087354873Z TS Packet size=2794 pts=5319063823 dts=-9223372036854775808 data_alignment_indicator=0

[acris5]

Ffmpeg generates several packages with 126000 pts at start and then starts passing real pts
input 126000 5474206969 leads to negative result

[acris5]

And I am not sure if it is correct to parse pts as signed int values.

[zaki699]

Hi @acris5,

PESContext in FFMPEG also uses signed integer type for storing the PTS/DTS.

typedef struct PESContext {
    int pid;
    int pcr_pid; /**< if -1 then all packets containing PCR are considered */
    int stream_type;
    MpegTSContext *ts;
    AVFormatContext *stream;
    AVStream *st;
    AVStream *sub_st; /**< stream for the embedded AC3 stream in HDMV TrueHD */
    enum MpegTSState state;
    /* used to get the format */
    int data_index;
    int flags; /**< copied to the AVPacket flags */
    int PES_packet_length;
    int pes_header_size;
    int extended_stream_id;
    uint8_t stream_id;
    int64_t pts, dts;
    int64_t ts_packet_pos; /**< position of first TS packet of this PES packet */
    uint8_t header[MAX_PES_HEADER_SIZE];
    AVBufferRef *buffer;
    SLConfigDescr sl;
    int merged_st;
} PESContext;

The issue must come from somewhere else.