Why can't I reorder the streams in my mpg container with ffmpeg?

Tricky one this seemed at first. I wondered if this old FFmpeg trac ticket might hold the key:

There is no stream order in mpeg-ps. what you see from ffmpeg output order is likely just if a audio or video packet comes first

But that's not actually the problem; however it is worth noting that your file has a .mpg extension, when you should be trying to output an MP4 or MKV. ".mpg" is only valid if it contains legacy MPEG-1 and MPEG-2 formats. H.264 or AAC elementary streams are invalid.

If you've not created this file yourself, it's either a mislabelled container (e.g. MKV or MP4), or someone has bizarrely muxed the streams to .mpg. Note how FFmpeg warns you of the incompatible codec during your stream reorder attempt.

MPEG-PS is a packetised format, so there's no elementary streams as such. If it's genuinely an MPEG-PS file, it may be that an audio sample appears first. Either way, you should abandon using .mpg for your formats.

See the end of this answer for how you can use FFprobe to fairly accurately identify the actual container format.

I had another think, and finally a neuron reminded me about how the -map output follows the order of assignment.

An important thing to note is that -map 0:v -map 0:a doesn't quite work how you might expect it with files containing more than one of a stream type, as that syntax matches all applicable streams of that type.

Gyan has clarified that if you have a file with exactly one video and one audio stream, -map 0:v -map 0:a will function equivalently to -map 0:1 -map 0:0.

If you want to use the 0:a syntax, if you have more than one audio for example you must address them individually, otherwise FFmpeg will group them when reordering. -map 0:a will move both audios; -map 0:a:0 will move just the first audio.

The alternative, remembering to always check stream order in every file you manipulate, is to specify absolute stream numbers in the order you wish to have them in the output. So, -map 0:1 -map 0:0 if your video is the second of two streams in the source file.

For files with one video and one audio stream, you can use either method.

Tests

I created an .MP4 file containing one H.264 video as stream 0:0 and one MP3 audio as stream 0:1.

Original file:

Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'C:\temp\video-audio.mp4':
  Metadata:
    major_brand     : isom
    minor_version   : 512
    compatible_brands: isomiso2avc1mp41
    encoder         : Lavf58.78.100
  Duration: 00:05:00.30, start: 0.000000, bitrate: 422 kb/s
  Stream #0:0(und): Video: h264 (Main) (avc1 / 0x31637661), yuv420p(tv, bt709), 1920x1080 [SAR 1:1 DAR 16:9], 421 kb/s, 23.98 fps, 23.98 tbr, 11988 tbn, 47.95 tbc (default)
    Metadata:
      handler_name    : GPAC ISO Video Handler
      vendor_id       : [0][0][0][0]
  Stream #0:1(und): Audio: mp3 (mp4a / 0x6134706D), 44100 Hz, stereo, fltp, 180 kb/s (default)
    Metadata:
      handler_name    : SoundHandler
      vendor_id       : [0][0][0][0]

Then I fed it back to FFmpeg:

ffmpeg -i C:\temp\video-audio.mp4 -map 0:1 -map 0:0 -c copy C:\temp\swapped.mp4
(equivalent to -map 0:a -map 0:v in this case)

Result: swapped streams; MP3 audio stream is 0:0, H.264 video stream is 0:1

Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'C:\temp\swapped.mp4':
  Metadata:
    major_brand     : isom
    minor_version   : 512
    compatible_brands: isomiso2avc1mp41
    encoder         : Lavf58.78.100
  Duration: 00:05:00.30, start: 0.000000, bitrate: 422 kb/s
  Stream #0:0(und): Audio: mp3 (mp4a / 0x6134706D), 44100 Hz, stereo, fltp, 180 kb/s (default)
    Metadata:
      handler_name    : SoundHandler
      vendor_id       : [0][0][0][0]
  Stream #0:1(und): Video: h264 (Main) (avc1 / 0x31637661), yuv420p(tv, bt709), 1920x1080 [SAR 1:1 DAR 16:9], 421 kb/s, 23.98 fps, 23.98 tbr, 11988 tbn, 47.95 tbc (default)
    Metadata:
      handler_name    : GPAC ISO Video Handler
      vendor_id       : [0][0][0][0]

This appears to accomplish what you want :-)

ffmpeg -i INPUTFILE -map 0:1 -map 0:0 -c copy OUTPUTFILE.mp4 or
ffmpeg -i INPUTFILE -map 0:v -map 0:a -c copy OUTPUTFILE.mp4

Reminder:

• For files with one video and one audio stream, you can use either method above.
• For files with multiple audios or videos, determine the stream index and specify using the more granular 0:v:0, 0:a:0 syntax.

ffmpeg -i INPUTFILE shows a file's numeric stream IDs, and this may be quicker for the odd file. However, numeric references skips the sanity check of specifying only audio, video, subtitles etc. when reordering.

FFmpeg's Stream Specifiers and Advanced Options documentation is worth bookmarking.

Further reading:

• FFmpeg Trac documentation for -map and their main documentation for -map.
• This previous Q&A on Video.SE, which in turn references this answer which talks about the -disposition switch. NB that -disposition is used for indicating which streams the player 'should' consider as default (Section 5.4, "Main Options" in the FFmpeg docs), not doing any physical stream reordering.

(big thanks to Gyan for being so observant!)

Using FFprobe to identify container

FFprobe can do a best-effort detection of the real container format, ignoring the extension. Here's an example of my demo "swapped.mp4", renamed to .mpg:

ffprobe -hide_banner -show_error -show_format -i "C:\temp\swapped.mpg"
Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'C:\temp\swapped.mpg':
  Metadata:
    major_brand     : isom
    minor_version   : 512
    compatible_brands: isomiso2avc1mp41
    encoder         : Lavf58.78.100
  Duration: 00:05:00.30, start: 0.000000, bitrate: 422 kb/s
  Stream #0:0(und): Audio: mp3 (mp4a / 0x6134706D), 44100 Hz, stereo, fltp, 180 kb/s (default)
    Metadata:
      handler_name    : SoundHandler
      vendor_id       : [0][0][0][0]
  Stream #0:1(und): Video: h264 (Main) (avc1 / 0x31637661), yuv420p(tv, bt709), 1920x1080 [SAR 1:1 DAR 16:9], 421 kb/s, 23.98 fps, 23.98 tbr, 11988 tbn, 47.95 tbc (default)
    Metadata:
      handler_name    : GPAC ISO Video Handler
      vendor_id       : [0][0][0][0]
[FORMAT]
filename=C:\temp\swapped.mpg
nb_streams=2
nb_programs=0
format_name=mov,mp4,m4a,3gp,3g2,mj2
format_long_name=QuickTime / MOV
start_time=0.000000
duration=300.301000
size=15847817
bit_rate=422184
probe_score=100
TAG:major_brand=isom
TAG:minor_version=512
TAG:compatible_brands=isomiso2avc1mp41
TAG:encoder=Lavf58.78.100
[/FORMAT]

Note major_brand=isom (ISO Base Media file format), format_name, format_long_name and so on.

A true MPEG-2 video I produced last month (a DVD rip) outputs this:

ffprobe -hide_banner -show_error -show_format -i "C:\temp\opera.mpg"
Input #0, mpeg, from 'C:\temp\opera.mpg':
  Duration: 02:15:23.71, start: 66240.530111, bitrate: 4194 kb/s
  Stream #0:0[0x1e0]: Video: mpeg2video (Main), yuv420p(tv, smpte170m, top first), 720x576 [SAR 64:45 DAR 16:9], 25 fps, 25 tbr, 90k tbn, 50 tbc
    Side data:
      cpb: bitrate max/min/avg: 7000000/0/0 buffer size: 1835008 vbv_delay: N/A
  Stream #0:1[0x80]: Audio: ac3, 48000 Hz, stereo, fltp, 192 kb/s
[FORMAT]
filename=C:\temp\opera.mpg
nb_streams=2
nb_programs=0
format_name=mpeg
format_long_name=MPEG-PS (MPEG-2 Program Stream)
start_time=66240.530111
duration=8123.712000
size=4259503237
bit_rate=4194637
probe_score=26
[/FORMAT]

FFprobe correctly reports format_name as mpeg and format_long_name as MPEG-PS.

Everything Chris said was right, and a big help. The original .MPG with H264 video inside came from TivoDecoder; I never thought to question whether that container was valid for that video format, and when QT was willing to play it, I figured the ffprobe warning wasn't a big deal. :)

Remuxing to an MP4 container gave me something Windows will play.

ffmpeg -hide_banner -ss 00:17:24 -i myfile.mpg -t 00:02:40 -c copy myfile.trimmed.mp4
[h264 @ 000002d5d73f4040] Increasing reorder buffer to 2
[mpegts @ 000002d5d73edbc0] PES packet size mismatch
[mpegts @ 000002d5d73edbc0] Packet corrupt (stream = 1, dts = 8467425232).
[mpegts @ 000002d5d73edbc0] Could not find codec parameters for stream 2 (Unknown: none ([151][0][0][0] / 0x0097)): unknown codec
Consider increasing the value for the 'analyzeduration' and 'probesize' options
[mpegts @ 000002d5d73edbc0] PES packet size mismatch
[mpegts @ 000002d5d73edbc0] Packet corrupt (stream = 1, dts = 8467425232).
Input #0, mpegts, from 'myfile.mpg':
  Duration: 00:30:00.63, start: 92282.982578, bitrate: 6249 kb/s
  Program 1
    Stream #0:0[0x1aab]: Video: h264 (High) ([27][0][0][0] / 0x001B), yuv420p(tv, progressive), 1280x720 [SAR 1:1 DAR 16:9], Closed Captions, 59.94 fps, 59.94 tbr, 90k tbn, 119.88 tbc
    Stream #0:1[0x1abf]: Audio: ac3 ([129][0][0][0] / 0x0081), 48000 Hz, 5.1(side), fltp, 384 kb/s
    Stream #0:2[0x1ac1]: Unknown: none ([151][0][0][0] / 0x0097)
[mp4 @ 000002d5d7e90540] track 1: codec frame size is not set
Output #0, mp4, to 'myfile.trimmed.mp4':
  Metadata:
    encoder         : Lavf58.45.100
    Stream #0:0: Video: h264 (High) (avc1 / 0x31637661), yuv420p(tv, progressive), 1280x720 [SAR 1:1 DAR 16:9], q=2-31, 59.94 fps, 59.94 tbr, 90k tbn, 90k tbc
    Stream #0:1: Audio: ac3 (ac-3 / 0x332D6361), 48000 Hz, 5.1(side), fltp, 384 kb/s
Stream mapping:
  Stream #0:0 -> #0:0 (copy)
  Stream #0:1 -> #0:1 (copy)
Press [q] to stop, [?] for help
frame= 9570 fps=0.0 q=-1.0 Lsize=  122587kB time=00:02:39.99 bitrate=6276.6kbits/s speed= 462x
video:114772kB audio:7545kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: 0.220873%

ffprobe -hide_banner -show_error -show_format -i myfile.trimmed.mp4
Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'myfile.trimmed.mp4':
  Metadata:
    major_brand     : isom
    minor_version   : 512
    compatible_brands: isomiso2avc1mp41
    encoder         : Lavf58.45.100
  Duration: 00:02:40.96, start: 0.000000, bitrate: 6239 kb/s
    Stream #0:0(und): Video: h264 (High) (avc1 / 0x31637661), yuv420p(tv), 1280x720 [SAR 1:1 DAR 16:9], Closed Captions, 5890 kb/s, 59.94 fps, 59.94 tbr, 90k tbn, 119.88 tbc (default)
    Metadata:
      handler_name    : VideoHandler
    Stream #0:1(und): Audio: ac3 (ac-3 / 0x332D6361), 48000 Hz, 5.1(side), fltp, 384 kb/s (default)
    Metadata:
      handler_name    : SoundHandler
    Side data:
      audio service type: main
[FORMAT]
filename=myfile.trimmed.mp4
nb_streams=2
nb_programs=0
format_name=mov,mp4,m4a,3gp,3g2,mj2
format_long_name=QuickTime / MOV
start_time=0.000000
duration=160.960000
size=125529106
bit_rate=6239021
probe_score=100
TAG:major_brand=isom
TAG:minor_version=512
TAG:compatible_brands=isomiso2avc1mp41
TAG:encoder=Lavf58.45.100
[/FORMAT]

I've got a new problem with the video and audio being massively out of sync, but I'll ask that as a separate question.

It's very tricky but possible to reorder audio streams with ffmpeg tool. If you know the source streams' numbers, or their ids just map them in order you want: ffmpeg -i "..." -map 0:a:0,0:1 -map 0:a:1,0:1 ... or use -map i:0xbbbb -map i:0xaaaa ... i.e. the -map commands allows to select new order of your audio streams.

The more tricky is if you want to reorder them based on their language: imagine your source contains English, French and Spanish (and possible other) audio tracks, and you want to order them as French, English, Spanish, and any other languages following. So based on -map command you can do the following: ffmpeg -i "..." -map 0:V,0:0 -map 0:m:language:fre? 0:m:language:eng? 0:m:language:spa? -map 0:a? -map -0:s? .... a little explanation of parameters: first map real video stream (capital V) as target stream 0 (you can change this), then search for stream with metadata's language French and if it exists (the question mark at end) put as first audio stream, repeat the same with other requested languages, but before finish map any other(s) stream in case there is no any of your requested languages or won't loose some source audio stream, and finally (very important in some cases) delete mapping of subtitles because the metadata for subtitles is same as metadata for audio streams, and if there is subtitle stream for French but no audio stream for French the result will be subtitle stream mapped and no audio stream - this depends on your requirements of course.

Do not forget that using -map command prevent automatically mapping all stream(s) to target, that's why '-map 0:v' is placed in command, the same is true for data and and download streams too. The question marks at end of any audio streams selection allows absent of exact audio stream, so the ffmpeg command will not stops with error.

Note: it's possible mapping commands to duplicate your audio stream(s) in output...