现在接口还不是很完善, 由于我需要 output format 的 custom io, 需要实现: 不输出到文件(即文件名是null), 指定format 比如为mp4, 我需要用 custom io, 在输出format时, 拿到输出的所有数据做别的处理. 现在我的做法是修改了rsmpeg源码, 可以满足我的需求, 但是希望源码可以直接可以满足需求:

我的用法:

非常感谢这个库, 整体还是很好用~

想用rsmpeg 实现下面的功能，因为ffmpeg 是lgpl 协议所有没有libx264 依赖。 ./ffmpeg -r 30 -i xxxx.h264 -c:v copy -f mp4 xxxxx.mp4

基于tests/avio_writing.rs 删除了decode 和encode 部分， 但是无法通过 AVframe去设置 pts 时间，导致程序报错，请给一些建议。

图片来自此连接-章节2-重新封装

I want to achieve split screen effect, at the beginning, I will associate multiple inputs in the filter. but I can't do it, because of the wrong

outputs.next = video1_outputs.as_mut_ptr();

cannot assign to data in a dereference of `rsmpeg::avfilter::AVFilterInOut`
trait `DerefMut` is required to modify through a dereference, but it is not implemented for `rsmpeg::avfilter::AVFilterInOut`

the main code:

// 创建buffer, 用于接收输入
let buffer_src = AVFilter::get_by_name(cstr!("buffer")).unwrap();

// video0: 创建 filter 上下文, 关联 输入的 buffer
let mut buffer_src_context =
  filter_graph.create_filter_context(&buffer_src, cstr!("video0"), Some(args))?;
// video0: 分配 filter 的输入, 关联 创建的 filter 上下文
let mut outputs = AVFilterInOut::new(cstr!("video0"), &mut buffer_src_context, 0);

// video1: 创建 filter 上下文, 关联 输入的 buffer
let mut buffer_src_context =
  filter_graph.create_filter_context(&buffer_src, cstr!("video1"), Some(args))?;
// video1: 分配 filter 的输入, 关联 创建的 filter 上下文
let mut video1_outputs = AVFilterInOut::new(cstr!("video1"), &mut buffer_src_context, 0);

// 关联 多个输入
outputs.next = video1_outputs.as_mut_ptr();
// outputs.next = video1_outputs.into_raw().as_ptr();

in rsmpeg: wrap!(AVFilterInOut: ffi::AVFilterInOut); this is: wrap_pure!(($name): $ffi_type $(,$attach: $attach_type = $attach_default)*); and this implements

pub fn as_mut_ptr(&mut self) -> *mut $ffi_type {
   self.something_should_not_be_touched_directly.as_ptr()
}

but why can't it --> outputs.next = video1_outputs.as_mut_ptr();

video.mp4

下载这个 mp4，替换 tests/assets/vids/bear.mp4，然后执行 thumbnail 测试：

wget https://user-images.githubusercontent.com/1524609/131678290-c6b90aee-d018-4078-99b4-45cc410bd67b.mp4 -O video.mp4
cp video.mp4 tests/assets/vids/bear.mp4
cargo test --test thumbnail

会得到如下错误：

    Finished test [unoptimized + debuginfo] target(s) in 0.04s
     Running tests/thumbnail.rs (target/debug/deps/thumbnail-fb8cd98fade3377b)

running 1 test
test thumbnail_test ... FAILED

failures:

---- thumbnail_test stdout ----
thread 'thumbnail_test' panicked at 'called `Result::unwrap()` on an `Err` value: Cannnot find video cover packet', tests/thumbnail.rs:132:6
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace


failures:
    thumbnail_test

test result: FAILED. 0 passed; 1 failed; 0 ignored; 0 measured; 0 filtered out; finished in 0.00s

error: test failed, to rerun pass '--test thumbnail'

For proper video rendering, we need to know the stride, but that involves having info about the pixel format, which is stored into

https://docs.rs/rsmpeg/0.8.0/rsmpeg/ffi/struct.AVPixFmtDescriptor.html

is there a way to get this information in rsmpeg given a frame.format number?

Hello,

The last version of rsmpeg (0.6.0) doesn't seem to compile:

error[E0425]: cannot find function `av_gcd_q` in module `ffi`
    --> /home/lorenzo/.cargo/registry/src/github.com-1ecc6299db9ec823/rsmpeg-0.6.0/src/avutil/rational.rs:65:19
     |
65   |     unsafe { ffi::av_gcd_q(a, b, max_den, def) }
     |                   ^^^^^^^^
     |
    ::: /home/lorenzo/Scrivania/Varie/repo/remotia/target/debug/build/rusty_ffmpeg-f322e92cb20dcce1/out/binding.rs:6392:5
     |
6392 |     pub fn av_add_q(b: AVRational, c: AVRational) -> AVRational;
     |     ------------------------------------------------------------ similarly named function `av_add_q` defined here
     |
help: a function with a similar name exists
     |
65   |     unsafe { ffi::av_add_q(a, b, max_den, def) }
     |                   ~~~~~~~~
help: consider importing this function
     |
1    | use crate::avutil::av_gcd_q;error[E0425]: cannot find function `av_gcd_q` in module `ffi`
    --> /home/lorenzo/.cargo/registry/src/github.com-1ecc6299db9ec823/rsmpeg-0.6.0/src/avutil/rational.rs:65:19
     |
65   |     unsafe { ffi::av_gcd_q(a, b, max_den, def) }
     |                   ^^^^^^^^
     |
    ::: /home/lorenzo/Scrivania/Varie/repo/remotia/target/debug/build/rusty_ffmpeg-f322e92cb20dcce1/out/binding.rs:6392:5
     |
6392 |     pub fn av_add_q(b: AVRational, c: AVRational) -> AVRational;
     |     ------------------------------------------------------------ similarly named function `av_add_q` defined here
     |
help: a function with a similar name exists
     |
65   |     unsafe { ffi::av_add_q(a, b, max_den, def) }
     |                   ~~~~~~~~
help: consider importing this function
     |
1    | use crate::avutil::av_gcd_q;
     |
     |

I've tried downgrading the ffmpeg release to 4.3 but it doesn't seem to work.

rustc --version output is:

rustc 1.56.1 (59eed8a2a 2021-11-01)

I'm trying to implement AVBitStreamFilter in this library. I have a little code so far but I'm not sure if I'm working in the right direction. AVBitStreamFilter was easy but AVBSFContext has a bit of a strange allocation method and I couldn't find another example like it in your code.

Would you mind taking a look and letting me know if I'm doing anything wrong? This is what I have so far.

use std::{ffi::CStr, mem::MaybeUninit, ptr::NonNull};

use crate::{
    error::{Result, RsmpegError},
    ffi,
    shared::PointerUpgrade,
};

wrap!(AVBitStreamFilter: ffi::AVBitStreamFilter);

impl AVBitStreamFilter {
    /// Find a bitstream filter instance with it's short name.
    pub fn find_decoder_by_name(name: &CStr) -> Option<AVBitStreamFilter> {
        unsafe { ffi::av_bsf_get_by_name(name.as_ptr()) }
            .upgrade()
            .map(|x| unsafe { AVBitStreamFilter::from_raw(x) })
    }
}

wrap!(AVBSFContext: ffi::AVBSFContext);

impl AVBSFContext {
    /// Create a new [`AVBSFContext`] instance, allocate private data and
    /// initialize defaults for the given [`AVBitStreamFilter`].
    pub fn new(filter: &AVBitStreamFilter) -> Result<Self> {
        let mut bsfc_raw: MaybeUninit<ffi::AVBSFContext> = MaybeUninit::uninit();

        match unsafe { ffi::av_bsf_alloc(filter.as_ptr(), &mut bsfc_raw.as_mut_ptr()) } {
            0 => {
                let bsfc = unsafe {
                    AVBSFContext::from_raw(NonNull::new(&mut bsfc_raw.assume_init()).unwrap())
                };
                Ok(bsfc)
            }
            e => Err(RsmpegError::AVError(e)),
        }
    }
}

pub fn iformat(&'stream self) -> AVInputFormatRef<'stream> {
    unsafe { AVInputFormatRef::from_raw(NonNull::new(self.iformat).unwrap()) }
}

As the above example code, self.iformat maybe a null pointer cause panic at runtime, consider a new approach:

pub fn iformat(&'stream self) -> Option<AVInputFormatRef<'stream>> {
    unsafe { NonNull::new(self.iformat).map(AVInputFormatRef::from_raw) }
}

at https://github.com/larksuite/rsmpeg/blob/master/src/avutil/frame.rs#L76, these two

    pub fn data_mut(&mut self) -> &mut [*mut u8; 8] {
        unsafe { &mut self.deref_mut().data }
    }

    pub fn linesize_mut(&mut self) -> &mut [libc::c_int; 8] {
        unsafe { &mut self.deref_mut().linesize }
    }

are mutable. Can I do versions for &self? Also, why it returns &mut [*mut u8; 8] and not &mut [&mut[u8]]? I have to rely on usafe outside of the library to do std::slice::from_raw_parts (is it even safe?)

No really sure how to do error handling for send and receive packet. I know the FFI functions return i32 but I'm not sure how to make that a useful error in rsmpeg other than AVError(i32).

想生成FMP4 方便在游览器上观看： 实现类似的效果: ffmpeg.exe -i test.264 -f mp4 -movflags frag_keyframe+empty_moov output.mp4 我看其他教程，用C语言时候，写入文件格式头信息的时候设置AVDictionary结构体

AVDictionary *opts = NULL;
av_dict_set(&opts, "movflags", "frag_keyframe+empty_moov", 0);
avformat_write_header(o_fmt_ctx, &opts);
av_dict_free(&opts);

但是，我看了源码rsmpeg的话默认设置null

pub fn write_header(&mut self) -> Result<()> {
        unsafe { ffi::avformat_write_header(self.as_mut_ptr(), ptr::null_mut()) }
            .upgrade()
            .map_err(RsmpegError::WriteHeaderError)?;

        Ok(())
    }

我对ffmpeg不是很了解，是不是还有其他方法呢？请教一下。