Can we implement `Source::total_duration` for non-wav sources?

[icefoxen]

The question was brought up by this ggez issue: ggez/ggez#477 Edit for clarification: Basically, we just want to be able to find the duration of the decoded stream without having to actually decode the whole thing.

It does indeed appear to be correct that only the WAV decoder implements this method. rodio's stream-based API does seem like it might be problematic, but the method only exists when the stream is Seek, so I think we can manage it.

Looking at the various upstream crates, does the functionality exist to do this without having to decode the entire stream in the process?

• lewton: https://docs.rs/lewton/0.9.1/lewton/audio/fn.get_decoded_sample_count.html
• minimp3: Doesn't look like it, though I am pretty darn sure that the C library provides the capability to do this. Just need to write a function that skims through the blocks in the stream reading the metadata without bothering to decode the individual blocks.
• claxon: I think this has the relevant info, but it doesn't seem reliable (the samples field is an Option) and I'm not sure if there's a nicer way to get to it

[est31]

I'd recommend against using get_decoded_sample_count. There are better methods.

I've added the function so that you can prepare data structures in advance, or do similar things. If you use the function to get the total length of a file you'd still have to pass every single vorbis packet to that function, and you won't be able to use the inside_ogg glue code layer. In the end, even though it doesn't decode the file, it would still be an O(n) operation, where n corresponds to the number of packets which is coupled to the total length of the sample.

A much cheaper/better method is to use my ogg_metadata crate. It provides information about the total length of a vorbis file in its metadata struct.

[ryankopf]

How is this still an issue?

[gulis1]

My application needs Source::total_duration implemented for vorbis files. Can I work on a PR to implement this, using the ogg_metadata crate?

[yara-blue]

hi @gulis good news, we actually have total_duration implemented for the symphonia decoders. It should just work. Let me know if it does not!

[gulis1]

Hello @dvdsk, ty for answering so fast!!

I've tried enabling the symphonia and symphonia-all features, but rodio::Decoder::new returns the following error:

thread 'main' panicked at src/main.rs:13:60:
called `Result::unwrap()` on an `Err` value: IoError("end of stream")

Without enabling the Symphonia features, the vorbis file (/assets/music.ogg from this repo) plays, but Source::total_duration does not work.

This is the code I'm using for the test:

use std::error::Error;
use std::io::BufReader;
use rodio::{OutputStream, Sink};

fn main() -> Result<(), Box<dyn Error>> {

    let (_stream, stream_handle) = OutputStream::try_default()?;
    let sink = Sink::try_new(&stream_handle)?;
       
    let file = std::fs::File::open("assets/music.ogg").unwrap();
    sink.append(rodio::Decoder::new(BufReader::new(file)).unwrap());
    sink.sleep_until_end();

    Ok(())
}

And this is the Cargo.toml file:

[package]
name = "oggtest"
version = "0.1.0"
edition = "2021"

[dependencies]
rodio = { version = "0.20.1", features = ["symphonia", "symphonia-all"], default-features = false }

These are the first lines Symphonia is logging via the log crate:

[DEBUG symphonia_core::probe] found a possible format marker within [ff, ff, ff, ff, 0, 71, 2, 0, ff, ff, ff, ff, b8, 1, 4f, 67] @ 0+46 bytes.
[INFO  symphonia_core::probe] found the format marker [ff, ff] @ 0+46 bytes.
[WARN  symphonia_bundle_mp3::demuxer] invalid mpeg audio header
[WARN  symphonia_bundle_mp3::demuxer] skipping junk at 54 bytes
[WARN  symphonia_bundle_mp3::demuxer] invalid mpeg audio header
[WARN  symphonia_bundle_mp3::demuxer] invalid mpeg audio header
[WARN  symphonia_bundle_mp3::demuxer] skipping junk at 19972 bytes
...

I've tried various combinations of features, but I haven't managed to get it working. Maybe I'm not understanding properly how they work?

[gulis1]

Alright, sorry about the confusion.

I fixed the issue in the previous comment by adding Symphonia to my project's dependencies (is this the intended behaviour?):

Cargo.toml

[package]
name = "oggtest"
version = "0.1.0"
edition = "2021"

[dependencies]
rodio = { version = "0.20.1", features = ["symphonia", "symphonia-all"], default-features=false }
symphonia = "0.5.4"

Sadly, even after this Source::total_duration doesn't work for me. It looks like the issue is in the SymphoniaDecoder::init function (file /src/decoder/symphonia.rs), in line 107:

let total_duration = stream
            .codec_params
            .time_base
            .zip(stream.codec_params.n_frames)               // stream.codec_params.n_frames is None here
            .map(|(base, frames)| base.calc_time(frames));

[yara-blue]

I've tried enabling the symphonia and symphonia-all features, but rodio::Decoder::new returns the following error:

thread 'main' panicked at src/main.rs:13:60:
called `Result::unwrap()` on an `Err` value: IoError("end of stream")

I just wrote a test and you are right! this is not working :(

I fixed the issue in the previous comment by adding Symphonia to my project's dependencies (is this the intended behaviour?):

Very much not! I'm kinda surprised that worked 😅

I just remember @roderickvd mentioning making the symphonia decoders more robust (see: #678 (comment)). Maybe that work will fix this too.

If you would like to have a go at fixing this please go ahead and have fun 👍

[yara-blue]

also lets move this to its own issue: #696

[roderickvd]

I just remember @roderickvd mentioning making the symphonia decoders more robust (see: #678 (comment)). Maybe that work will fix this too.

Yes. Beyond the feature flags, the audio specifications can be None for some codecs until the first packet is decoded. So that needs fixing.