https://github.com/eyevinn/mp4ff
Library and tools for working with MP4 files containing video, audio, subtitles, or metadata. The focus is on fragmented files. Includes mp4ff-info, mp4ff-encrypt, mp4ff-decrypt and other tools.
https://github.com/eyevinn/mp4ff
aac ac-3 adts avc cmaf ec-3 fmp4 fragmented-mp4-files h264 hevc isobmff mp4 mpeg-dash pps sei sps stpp video vp9 wvtt
Last synced: 9 days ago
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Library and tools for working with MP4 files containing video, audio, subtitles, or metadata. The focus is on fragmented files. Includes mp4ff-info, mp4ff-encrypt, mp4ff-decrypt and other tools.
- Host: GitHub
- URL: https://github.com/eyevinn/mp4ff
- Owner: Eyevinn
- License: mit
- Created: 2020-01-30T16:41:52.000Z (over 5 years ago)
- Default Branch: master
- Last Pushed: 2025-04-08T13:30:19.000Z (6 months ago)
- Last Synced: 2025-04-13T15:00:06.937Z (6 months ago)
- Topics: aac, ac-3, adts, avc, cmaf, ec-3, fmp4, fragmented-mp4-files, h264, hevc, isobmff, mp4, mpeg-dash, pps, sei, sps, stpp, video, vp9, wvtt
- Language: Go
- Homepage:
- Size: 4.45 MB
- Stars: 515
- Watchers: 19
- Forks: 95
- Open Issues: 2
-
Metadata Files:
- Readme: README.md
- Changelog: CHANGELOG.md
- License: LICENSE
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[](https://app.osaas.io/browse/eyevinn-mp4ff)
Module mp4ff implements MP4 media file parsing and writing for AVC and HEVC video, AAC and AC-3 audio, stpp and wvtt subtitles, and
timed metadata tracks.
It is focused on fragmented files as used for streaming in MPEG-DASH, MSS and HLS fMP4, but can also decode and encode all
boxes needed for progressive MP4 files.
## Command Line Tools
Some useful command line tools are available in [cmd](cmd) directory.
1. [mp4ff-info](cmd/mp4ff-info) prints a tree of the box hierarchy of a mp4 file with information
about the boxes.
2. [mp4ff-pslister](cmd/mp4ff-pslister) extracts and displays SPS and PPS for AVC or HEVC in a mp4 or a bytestream (Annex B) file.
Partial information is printed for HEVC.
3. [mp4ff-nallister](cmd/mp4ff-nallister) lists NALUs and picture types for video in progressive or fragmented file
4. [mp4ff-subslister](cmd/mp4ff-subslister) lists details of wvtt or stpp (WebVTT or TTML in ISOBMFF) subtitle samples
5. [mp4ff-crop](cmd/mp4ff-crop) crops a **progressive** mp4 file to a specified duration
6. [mp4ff-encrypt](cmd/mp4ff-encrypt) encrypts a fragmented file using cenc or cbcs Common Encryption scheme
7. [mp4ff-decrypt](cmd/mp4ff-decrypt) decrypts a fragmented file encrypted using cenc or cbcs Common Encryption scheme
You can install these tools by going to their respective directory and run `go install .` or directly from the repo with
go install github.com/Eyevinn/mp4ff/cmd/mp4ff-info@latest
go install github.com/Eyevinn/mp4ff/cmd/mp4ff-encrypt@latest
...
for each individual tool.
## Codec support
This repo is focused on the file format, but goes beyond the base file format and supports
codec-specific boxes. The codecs and their boxes are
| Type| Codec | Sample Entry | Config Box | Other Boxes |
| ----- | ----| ---- | ---- | ---- |
| Video | AVC/H.264 | avc1, avc3 | avcC | btrt, pasp, colr |
| Video | HEVC/H.265 | hvc1, hev1 | hvcC | btrt, pasp, colr |
| Video | AV1 | av01 | av1C | btrt, pasp, colr |
| Video | AVS3 | avs3 | av3c | btrt, pasp, colr |
| Video | VP8/VP9 | vp08, vp09 | vpcC | btrt, pasp, colr |
| Video | VVC/H.266 | vvc1, vvi1 | vvcC | btrt, pasp, colr |
| Video | Encrypted | encv | sinf | btrt |
| Audio | AAC | mp4a | esds | btrt |
| Audio | AC-3 | ac-3 | dac3 | btrt |
| Audio | E-AC-3 | ec-3 | dec3 | btrt |
| Audio | AC-4 | ac-4 | dac4 | btrt |
| Audio | Opus | Opus | dOps | btrt |
| Audio | MPEG-H 3D Audio | mha1, mha2, mhm1, mhm2 | mhaC | btrt |
| Audio | Encrypted | enca | sinf | btrt |
| Subtitles | WebVTT | wvtt | vttC, vlab | vttc, vtte, vtta, vsid, ctim, iden, sttg, payl, btrt |
| Subtitles | TTML | stpp | - | btrt |
| Subtitles | Generic | evte | - | btrt |
## Open Source Cloud
You can also run the tools as a job in [Eyevinn Open Source Cloud](https://app.osaas.io/dashboard/service/eyevinn-mp4ff). Here is an example using the `mp4ff-crop` command and the Open Source Cloud CLI.
```bash
% export OSC_ACCESS_TOKEN=
% npx -y @osaas/cli@latest create eyevinn-mp4ff test \
-o awsAccessKeyId= \
-o awsSecretAccessKey= \
-o s3EndpointUrl=https://eyevinnlab-birme.minio-minio.auto.prod.osaas.io \
-o cmdLineArgs="mp4ff-crop s3://input/VINN.mp4 s3://output/VINN-crop2.mp4"
```
The file VINN.mp4 on the bucket called "input" on the MinIO server at https://eyevinnlab-birme.minio-minio.auto.prod.osaas.io is processed and output uploaded to bucket "output" on the same MinIO server.
## Example code
Example code for some common use cases is available in the [examples](examples) directory.
The examples and their functions are:
1. [initcreator](examples/initcreator) creates typical init segments (ftyp + moov) for different video and
audio codecs
2. [resegmenter](examples/resegmenter) reads a segmented file (CMAF track) and resegments it with other
segment durations using `FullSample`
3. [segmenter](examples/segmenter) takes a progressive mp4 file and creates init and media segments from it.
This tool has been extended to support generation of segments with multiple tracks as well
as reading and writing `mdat` in lazy mode
4. [multitrack](examples/multitrack) parses a fragmented file with multiple tracks
5. [combine-segs](examples/combine-segs) combines single-track init and media segments into multi-track segments
6. [add-sidx](examples/add-sidx) adds a top-level sidx box describing the segments of a fragmented files.
## Packages
The top-level packages in the mp4ff module are
1. [mp4](mp4) provides support for for parsing (called Decode) and writing (Encode) a plethor of mp4 boxes.
It also contains helper functions for extracting, encrypting, dectrypting samples and a lot more.
2. [avc](avc) deals with AVC (aka H.264) video in the `mp4ff/avc` package including parsing of SPS and PPS,
and finding start-codes in Annex B byte streams.
3. [hevc](hevc) provides structures and functions for dealing with HEVC video and its packaging.
4. [vvc](vvc) provides structures and functions for dealing with VVC video and its packaging.
5. [sei](sei) provides support for handling Supplementary Enhancement Information (SEI) such as timestamps
for AVC and HEVC video.
6. [av1](av1) provides basic support for AV1 video packaging
7. [aac](aac) provides support for AAC audio. This includes handling ADTS headers which is common
for AAC inside MPEG-2 TS streams.
8. [bits](bits) provides bit-wise and byte-wise readers and writers used by the other packages.
## Structure and usage
### mp4.File and its composition
The top level structure for both non-fragmented and fragmented mp4 files is `mp4.File`.
In a progressive (non-fragmented) `mp4.File`, the top-level attributes Ftyp, Moov, and Mdat point to the corresponding boxes.
A fragmented `mp4.File` can be more or less complete, like a single init segment,
one or more media segments, or a combination of both, like a CMAF track which renders
into a playable one-track asset. It can also have multiple tracks.
For fragmented files, the following high-level attributes are used:
* `Init` contains a `ftyp` and a `moov` box and provides the general metadata for a fragmented file.
It corresponds to a CMAF header. It can also contain one or more `sidx` boxes.
* `Segments` is a slice of `MediaSegment` which start with an optional `styp` box, possibly one or more `sidx`
boxes and then one or more`Fragment`s.
* `Fragment` is a mp4 fragment with exactly one `moof` box followed by a `mdat` box where the latter
contains the media data. It can have one or more `trun` boxes containing the metadata
for the samples. The fragment can start with one or more `emsg` boxes.
It should be noted that it is sometimes hard to decide what should belong to a Segment or Fragment.
All child boxes of container boxes such as `MoovBox` are listed in the `Children` attribute, but the
most prominent child boxes have direct links with names which makes it possible to write a path such
as
```go
fragment.Moof.Traf.Trun
```
to access the (only) `trun` box in a fragment with only one `traf` box, or
```go
fragment.Moof.Trafs[1].Trun[1]
```
to get the second `trun` of the second `traf` box (provided that they exist). Care must be
taken to assert that none of the intermediate pointers are nil to avoid `panic`.
### Creating new fragmented files
A typical use case is to generate a fragmented file consisting of an init segment
followed by a series of media segments.
The first step is to create the init segment. This is done in three steps as can be seen in
`examples/initcreator`:
```go
init := mp4.CreateEmptyInit()
init.AddEmptyTrack(timescale, mediatype, language)
init.Moov.Trak.SetHEVCDescriptor("hvc1", vpsNALUs, spsNALUs, ppsNALUs)
```
Here the third step fills in codec-specific parameters into the sample descriptor of the single track.
Multiple tracks are also available via the slice attribute `Traks` instead of `Trak`.
The second step is to start producing media segments. They should use the timescale that
was set when creating the init segment. Generally, that timescale should be chosen so that the
sample durations have exact values without rounding errors, e.g. 48000 for 48kHz audio.
A media segment contains one or more fragments, where each fragment has a `moof` and a `mdat` box.
If all samples are available before the segment is created, one can use a single
fragment in each segment. Example code for this can be found in `examples/segmenter`.
For low-latency MPEG-DASH generation, short-duration fragments are added to the segment as the
corresponding media samples become available.
A simple, but not optimal, way of creating a media segment is to first create a slice of `FullSample` with the data needed.
The definition of `mp4.FullSample` is
```go
mp4.FullSample{
Sample: mp4.Sample{
Flags uint32 // Flag sync sample etc
Dur uint32 // Sample duration in mdhd timescale
Size uint32 // Size of sample data
Cto int32 // Signed composition time offset
},
DecodeTime uint64 // Absolute decode time (offset + accumulated sample Dur)
Data []byte // Sample data
}
```
The `mp4.Sample` part is what will be written into the `trun` box.
`DecodeTime` is the media timeline accumulated time.
The `DecodeTime` value of the first sample of a fragment, will
be set as the `BaseMediaDecodeTime` in the `tfdt` box.
Once a number of such full samples are available, they can be added to a media segment like
```go
seg := mp4.NewMediaSegment()
frag := mp4.CreateFragment(uint32(segNr), mp4.DefaultTrakID)
seg.AddFragment(frag)
for _, sample := range samples {
frag.AddFullSample(sample)
}
```
This segment can finally be output to a `w io.Writer` as
```go
err := seg.Encode(w)
```
or to a `sw bits.SliceWriter` as
```go
err := seg.EncodeSW(sw)
```
For multi-track segments, the code is a bit more involved. Please have a look at `examples/segmenter`
to see how it is done. A more optimal way of handling media sample is
to handle them lazily, or using intervals, as explained next.
### Lazy decoding and writing of mdat data
For video and audio, the dominating part of a mp4 file is the media data which is stored
in one or more `mdat` boxes. In some cases, for example when segmenting large progressive
files, it is much more memory efficient to just read the movie or fragment metadata
from the `moov` or `moof` box and defer the reading of the media data from the `mdat` box
to later.
For decoding, this is supported by running `mp4.DecodeFile()` in lazy mode as
```go
parsedMp4, err = mp4.DecodeFile(ifd, mp4.WithDecodeMode(mp4.DecModeLazyMdat))
```
In this case, the media data of the `mdat` box will not be read, but only its size is being saved.
To read or copy the actual data corresponding to a sample, one must calculate the
corresponding byte range and either call
```go
func (m *MdatBox) ReadData(start, size int64, rs io.ReadSeeker) ([]byte, error)
```
or
```go
func (m *MdatBox) CopyData(start, size int64, rs io.ReadSeeker, w io.Writer) (nrWritten int64, err error)
```
Example code for this, including lazy writing of `mdat`, can be found in `examples/segmenter`
with the `lazy` mode set.
### More efficient I/O using SliceReader and SliceWriter
The use of the interfaces `io.Reader` and `io.Writer` for reading and writing boxes gives a lot of
flexibility, but is not optimal when it comes to memory allocation. In particular, the
`Read(p []byte)` method needs a slice `p` of the proper size to read data, which leads to a
lot of allocations and copying of data.
In order to achieve better performance, it is advantageous to read the full top level boxes into
one, or a few, slices and decode these.
To enable that mode, version 0.27 of the code introduced `DecodeSR(sr bits.SliceReader)`
methods to every box `` where `mp4ff.bits.SliceReader` is an interface.
For example, the `TrunBox` gets the method `DecodeTrunSR(sr bits.SliceReader)` in addition to its old
`DecodeTrun(r io.Reader)` method. The `bits.SliceReader` interface provides methods to read all kinds
of data structures from an underlying slice of bytes. It has an implementation `bits.FixedSliceReader`
which uses a fixed-size slice as underlying slice, but one could consider implementing a growing version
which would get its data from some external source.
The memory allocation and speed improvements achieved by this may vary, but should be substantial,
especially compared to versions before 0.27 which used an extra `io.LimitReader` layer.
Fur further reduction of memory allocation, use a buffered top-level reader, especially when
when reading the `mdat` box of a progressive file.
#### Benchmarks
To investigate the efficiency of the new SliceReader and SliceWriter methods, benchmarks have been done.
The benchmarks are defined in
the file `mp4/benchmarks_test.go` and `mp4/benchmarks_srw_test.go`.
For `DecodeFile`, one can see a big improvement by going from version
0.26 to version 0.27 which both use the `io.Reader` interface
but another big increase by using the `SliceReader` source.
The latter benchmarks are called `BenchmarkDecodeFileSR` but have
here been given the same name, for easy comparison.
Note that the allocations here refers to the heap allocations
that are done inside the benchmark loop. Outside that loop,
a slice is allocated to keep the input data.
For `EncodeFile`, one can see that v0.27 is actually worse
than v0.26 when used with the `io.Writer` interface. That is
because the code was restructured so that all writes go
via the `SliceWriter` layer in order to reduce code duplication.
However, if instead using the `SliceWriter` methods directly,
there is a big relative gain in allocations as can be seen in
the last column.
| name \ time/op | v0.26 | v0.27 | v0.27-srw |
| ------------------------ | ------ | ------ | --------- |
|DecodeFile/1.m4s-16 | 21.9µs | 6.7µs | 2.6µs |
|DecodeFile/prog_8s.mp4-16 | 143µs | 48µs | 16µs |
|EncodeFile/1.m4s-16 | 1.70µs | 2.14µs | 1.50µs |
|EncodeFile/prog_8s.mp4-16 | 15.7µs | 18.4µs | 12.9µs |
| name \ alloc/op | v0.26 | v0.27 | v0.27-srw |
| ------------------------ |------ | ------ | --------- |
DecodeFile/1.m4s-16 | 120kB | 28kB | 2kB |
DecodeFile/prog_8s.mp4-16 | 906kB | 207kB | 12kB |
EncodeFile/1.m4s-16 | 1.16kB | 1.39kB | 0.08kB |
EncodeFile/prog_8s.mp4-16 | 6.84kB | 8.30kB | 0.05kB |
| name \ allocs/op | v0.26 | v0.27 | v0.27-srw |
| ------------------------ |------ | ----- | --------- |
|DecodeFile/1.m4s-16 | 98.0 | 42.0 | 34.0 |
|DecodeFile/prog_8s.mp4-16 | 454 | 180 | 169 |
|EncodeFile/1.m4s-16 | 15.0 | 15.0 | 3.0 |
|EncodeFile/prog_8s.mp4-16 | 101 | 86 | 1 |
## More about mp4 boxes
The `mp4ff.mp4` contains a lot of box implementations.
### Box structure and interface
Most boxes have their own file named after the box, but in some cases, there may be multiple boxes
that have the same content, and the code file then has a generic name like
`mp4/visualsampleentry.go`.
There is an interface for boxes: `Box` specified in `mp4.box.go`,
The interfaces define common Box methods including encode (writing),
but not the decode (parsing) methods which have distinct names for each box type and are
dispatched from the parsed box name.
That dispatch based on box name is defined by the tables `mp4.decodersSR` and `mp4.decoders`
for the functions `mp4.DecodeBoxSR()` and `mp4.DecodeBox()`, respectively.
The `SR` variant should normally be used for better performance.
If a box name is unknown, it will result in an `UnknownBox` being created.
### How to implement a new box
To implement a new box `fooo`, the following is needed.
Create a file `fooo.go` and create a struct type `FoooBox`.
`FoooBox` must implement the Box interface methods:
```go
Type()
Size()
Encode(w io.Writer)
EncodeSW(sw bits.SliceWriter)
Info()
```
It also needs its own decode methods `DecodeFoooSR` and `DecodeFooo`,
which must be added in the `decodersSR` map and `decoders` map, respectively
For a simple example, look at the `PrftBox` in `prft.go`.
A test file `fooo_test.go` should also have a test using the method `boxDiffAfterEncodeAndDecode`
to check that the box information is equal after encoding and decoding.
## Direct changes of attributes
Many attributes are public and can therefore be changed in freely.
The advantage of this is that it is possible to write code that can manipulate boxes
in many different ways, but one must be cautious to avoid breaking links to sub boxes or
create inconsistent states in the boxes.
As an example, container boxes such as `TrafBox` have a method `AddChild` which
adds a box to `Children`, its slice of children boxes, but also sets a specific
member reference such as `Tfdt` to point to that box. If `Children` is manipulated
directly, that link may no longer be valid.
## Encoding modes and optimizations
For fragmented files, one can choose to either encode all boxes in a `mp4.File`, or only code
the ones which are included in the init and media segments. The attribute that controls that
is called `FragEncMode`.
Another attribute `EncOptimize` controls possible optimizations of the file encoding process.
Currently, there is only one possible optimization called `OptimizeTrun`.
It can reduce the size of the `TrunBox` by finding and writing default
values in the `TfhdBox` and omitting the corresponding values from the `TrunBox`.
Note that this may change the size of all ancestor boxes of `trun`.
## Sample Number Offset
Following the ISOBMFF standard, sample numbers and other numbers start at 1 (one-based).
This applies to arguments of functions and methods.
The actual storage in slices is zero-based, so sample nr 1 has index 0 in the corresponding slice.
## Contributing
When contributing to this project, please ensure that commit messages follow the [Conventional Commits](https://www.conventionalcommits.org/) specification. This helps maintain a consistent and readable commit history.
Examples of conventional commit messages:
- `feat: add support for VVC video codec`
- `fix: resolve memory leak in fragment processing`
- `docs: update API documentation for mp4.File`
- `chore: update dependencies to latest versions`
## Stability
The APIs should be fairly stable, but minor non-backwards-compatible changes may happen until version 1.
## Specifications
The main specification for the MP4 file format is the ISO Base Media File Format (ISOBMFF) standard
ISO/IEC 14496-12 7th edition 2021. Some boxes are specified in other standards, as should be commented
in the code.
## LICENSE
MIT, see [LICENSE](LICENSE).
Some code in pkg/mp4, comes from or is based on which has
`Copyright (c) 2015 Jean-François Bustarret`.
Some code in pkg/bits comes from or is based on
`Copyright (c) 2017 Taichi Nakashima`.
## ChangeLog and Versions
See [CHANGELOG.md](CHANGELOG.md).
## Support
Join our [community on Slack](http://slack.streamingtech.se) where you can post any questions regarding any of our open source projects. Eyevinn's consulting business can also offer you:
* Further development of this component
* Customization and integration of this component into your platform
* Support and maintenance agreement
Contact [sales@eyevinn.se](mailto:sales@eyevinn.se) if you are interested.
## About Eyevinn Technology
[Eyevinn Technology](https://www.eyevinntechnology.se) is an independent consultant firm specialized in video and streaming. Independent in a way that we are not commercially tied to any platform or technology vendor. As our way to innovate and push the industry forward we develop proof-of-concepts and tools. The things we learn and the code we write we share with the industry in [blogs](https://dev.to/video) and by open sourcing the code we have written.
Want to know more about Eyevinn and how it is to work here. Contact us at work@eyevinn.se!