What goes under the hood in the determination of a video file resolution (eg. .mts or .mp4 files)?
I'd like to know how the resolution of a movie file is determined at the lowest level. Given such a file as input, how do command line tools lime mediainfo, ffprobe etc. determine its resolution? Is it calculated on the fly, or is it already written in the metadata of the movie file itself? If the latter, and if the metadata does not exist, is it possible to calculate the resolution from the file itself?
We can focus on .mts and .mp4 files in the answer.
video mp4
asked Nov 12 at 6:50
forgodsakehold
654
add a comment |
I'd like to know how the resolution of a movie file is determined at the lowest level. Given such a file as input, how do command line tools lime mediainfo, ffprobe etc. determine its resolution? Is it calculated on the fly, or is it already written in the metadata of the movie file itself? If the latter, and if the metadata does not exist, is it possible to calculate the resolution from the file itself?
We can focus on .mts and .mp4 files in the answer.
video mp4
asked Nov 12 at 6:50
forgodsakehold
654
I would suppose it is included in the headers of said format.
– Vivick
Nov 12 at 7:00
add a comment |
I'd like to know how the resolution of a movie file is determined at the lowest level. Given such a file as input, how do command line tools lime mediainfo, ffprobe etc. determine its resolution? Is it calculated on the fly, or is it already written in the metadata of the movie file itself? If the latter, and if the metadata does not exist, is it possible to calculate the resolution from the file itself?
We can focus on .mts and .mp4 files in the answer.
video mp4
asked Nov 12 at 6:50
forgodsakehold
654
I'd like to know how the resolution of a movie file is determined at the lowest level. Given such a file as input, how do command line tools lime mediainfo, ffprobe etc. determine its resolution? Is it calculated on the fly, or is it already written in the metadata of the movie file itself? If the latter, and if the metadata does not exist, is it possible to calculate the resolution from the file itself?
We can focus on .mts and .mp4 files in the answer.
video mp4
video mp4
asked Nov 12 at 6:50
forgodsakehold
654
asked Nov 12 at 6:50
forgodsakehold
654
asked Nov 12 at 6:50
forgodsakehold
654
asked Nov 12 at 6:50
forgodsakehold
654
asked Nov 12 at 6:50
forgodsakehold
654
654
I would suppose it is included in the headers of said format.
– Vivick
Nov 12 at 7:00
add a comment |
I would suppose it is included in the headers of said format.
– Vivick
Nov 12 at 7:00
I would suppose it is included in the headers of said format.
– Vivick
Nov 12 at 7:00
I would suppose it is included in the headers of said format.
– Vivick
Nov 12 at 7:00
add a comment |
1 Answer
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A good source to look at for this type of info is the QuickTime Format specification as MP4 is largely the same as this, and the QuickTime document is nicely put together.
You can see there that the width and height in pixels of a track is included in a header 'atom' at the start of each track:
See here for more info: https://developer.apple.com/library/archive/documentation/QuickTime/QTFF/QTFFChap2/qtff2.html#//apple_ref/doc/uid/TP40000939-CH204-32963
The same information is available, albeit without the same diagrams, in the ISO 14496-1 Media Format specification, which is the standardised version and basis of mp4:
aligned(8) class TrackHeaderBox
extends FullBox(‘tkhd’, version, flags){
if (version==1) {
unsigned int(64) creation_time;
unsigned int(64) modification_time;
unsigned int(32) track_ID;
const unsigned int(32) reserved = 0;
unsigned int(64) duration;
} else { // version==0
unsigned int(32) creation_time;
unsigned int(32) modification_time;
unsigned int(32) track_ID;
const unsigned int(32) reserved = 0;
unsigned int(32) duration;
}
const unsigned int(32)[2] reserved = 0;
template int(16) layer = 0;
template int(16) alternate_group = 0;
template int(16) volume = {if track_is_audio 0x0100 else 0};
const unsigned int(16) reserved = 0;
template int(32)[9] matrix=
{ 0x00010000,0,0,0,0x00010000,0,0,0,0x40000000 };
// unity matrix
unsigned int(32) width;
unsigned int(32) height;
You can access that spec here (requires a click to accept license): https://standards.iso.org/ittf/PubliclyAvailableStandards/c068960_ISO_IEC_14496-12_2015.zip
answered Nov 13 at 11:56
Mick
11.9k12460
add a comment |
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1 Answer
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1 Answer
1
active
oldest
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A good source to look at for this type of info is the QuickTime Format specification as MP4 is largely the same as this, and the QuickTime document is nicely put together.
You can see there that the width and height in pixels of a track is included in a header 'atom' at the start of each track:
See here for more info: https://developer.apple.com/library/archive/documentation/QuickTime/QTFF/QTFFChap2/qtff2.html#//apple_ref/doc/uid/TP40000939-CH204-32963
The same information is available, albeit without the same diagrams, in the ISO 14496-1 Media Format specification, which is the standardised version and basis of mp4:
aligned(8) class TrackHeaderBox
extends FullBox(‘tkhd’, version, flags){
if (version==1) {
unsigned int(64) creation_time;
unsigned int(64) modification_time;
unsigned int(32) track_ID;
const unsigned int(32) reserved = 0;
unsigned int(64) duration;
} else { // version==0
unsigned int(32) creation_time;
unsigned int(32) modification_time;
unsigned int(32) track_ID;
const unsigned int(32) reserved = 0;
unsigned int(32) duration;
}
const unsigned int(32)[2] reserved = 0;
template int(16) layer = 0;
template int(16) alternate_group = 0;
template int(16) volume = {if track_is_audio 0x0100 else 0};
const unsigned int(16) reserved = 0;
template int(32)[9] matrix=
{ 0x00010000,0,0,0,0x00010000,0,0,0,0x40000000 };
// unity matrix
unsigned int(32) width;
unsigned int(32) height;
You can access that spec here (requires a click to accept license): https://standards.iso.org/ittf/PubliclyAvailableStandards/c068960_ISO_IEC_14496-12_2015.zip
answered Nov 13 at 11:56
Mick
11.9k12460
add a comment |
A good source to look at for this type of info is the QuickTime Format specification as MP4 is largely the same as this, and the QuickTime document is nicely put together.
You can see there that the width and height in pixels of a track is included in a header 'atom' at the start of each track:
See here for more info: https://developer.apple.com/library/archive/documentation/QuickTime/QTFF/QTFFChap2/qtff2.html#//apple_ref/doc/uid/TP40000939-CH204-32963
The same information is available, albeit without the same diagrams, in the ISO 14496-1 Media Format specification, which is the standardised version and basis of mp4:
aligned(8) class TrackHeaderBox
extends FullBox(‘tkhd’, version, flags){
if (version==1) {
unsigned int(64) creation_time;
unsigned int(64) modification_time;
unsigned int(32) track_ID;
const unsigned int(32) reserved = 0;
unsigned int(64) duration;
} else { // version==0
unsigned int(32) creation_time;
unsigned int(32) modification_time;
unsigned int(32) track_ID;
const unsigned int(32) reserved = 0;
unsigned int(32) duration;
}
const unsigned int(32)[2] reserved = 0;
template int(16) layer = 0;
template int(16) alternate_group = 0;
template int(16) volume = {if track_is_audio 0x0100 else 0};
const unsigned int(16) reserved = 0;
template int(32)[9] matrix=
{ 0x00010000,0,0,0,0x00010000,0,0,0,0x40000000 };
// unity matrix
unsigned int(32) width;
unsigned int(32) height;
You can access that spec here (requires a click to accept license): https://standards.iso.org/ittf/PubliclyAvailableStandards/c068960_ISO_IEC_14496-12_2015.zip
answered Nov 13 at 11:56
Mick
11.9k12460
add a comment |
A good source to look at for this type of info is the QuickTime Format specification as MP4 is largely the same as this, and the QuickTime document is nicely put together.
You can see there that the width and height in pixels of a track is included in a header 'atom' at the start of each track:
See here for more info: https://developer.apple.com/library/archive/documentation/QuickTime/QTFF/QTFFChap2/qtff2.html#//apple_ref/doc/uid/TP40000939-CH204-32963
The same information is available, albeit without the same diagrams, in the ISO 14496-1 Media Format specification, which is the standardised version and basis of mp4:
aligned(8) class TrackHeaderBox
extends FullBox(‘tkhd’, version, flags){
if (version==1) {
unsigned int(64) creation_time;
unsigned int(64) modification_time;
unsigned int(32) track_ID;
const unsigned int(32) reserved = 0;
unsigned int(64) duration;
} else { // version==0
unsigned int(32) creation_time;
unsigned int(32) modification_time;
unsigned int(32) track_ID;
const unsigned int(32) reserved = 0;
unsigned int(32) duration;
}
const unsigned int(32)[2] reserved = 0;
template int(16) layer = 0;
template int(16) alternate_group = 0;
template int(16) volume = {if track_is_audio 0x0100 else 0};
const unsigned int(16) reserved = 0;
template int(32)[9] matrix=
{ 0x00010000,0,0,0,0x00010000,0,0,0,0x40000000 };
// unity matrix
unsigned int(32) width;
unsigned int(32) height;
You can access that spec here (requires a click to accept license): https://standards.iso.org/ittf/PubliclyAvailableStandards/c068960_ISO_IEC_14496-12_2015.zip
answered Nov 13 at 11:56
Mick
11.9k12460
A good source to look at for this type of info is the QuickTime Format specification as MP4 is largely the same as this, and the QuickTime document is nicely put together.
You can see there that the width and height in pixels of a track is included in a header 'atom' at the start of each track:
See here for more info: https://developer.apple.com/library/archive/documentation/QuickTime/QTFF/QTFFChap2/qtff2.html#//apple_ref/doc/uid/TP40000939-CH204-32963
The same information is available, albeit without the same diagrams, in the ISO 14496-1 Media Format specification, which is the standardised version and basis of mp4:
aligned(8) class TrackHeaderBox
extends FullBox(‘tkhd’, version, flags){
if (version==1) {
unsigned int(64) creation_time;
unsigned int(64) modification_time;
unsigned int(32) track_ID;
const unsigned int(32) reserved = 0;
unsigned int(64) duration;
} else { // version==0
unsigned int(32) creation_time;
unsigned int(32) modification_time;
unsigned int(32) track_ID;
const unsigned int(32) reserved = 0;
unsigned int(32) duration;
}
const unsigned int(32)[2] reserved = 0;
template int(16) layer = 0;
template int(16) alternate_group = 0;
template int(16) volume = {if track_is_audio 0x0100 else 0};
const unsigned int(16) reserved = 0;
template int(32)[9] matrix=
{ 0x00010000,0,0,0,0x00010000,0,0,0,0x40000000 };
// unity matrix
unsigned int(32) width;
unsigned int(32) height;
You can access that spec here (requires a click to accept license): https://standards.iso.org/ittf/PubliclyAvailableStandards/c068960_ISO_IEC_14496-12_2015.zip
answered Nov 13 at 11:56
Mick
11.9k12460
answered Nov 13 at 11:56
Mick
11.9k12460
answered Nov 13 at 11:56
Mick
11.9k12460
answered Nov 13 at 11:56
Mick
11.9k12460
11.9k12460
add a comment |
add a comment |
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I would suppose it is included in the headers of said format.
– Vivick
Nov 12 at 7:00