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// Copyright 2022 The ChromiumOS Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
//! This module implements a lightweight and safe decoder interface over `libavcodec`. It is
//! designed to concentrate all calls to unsafe methods in one place, while providing the same
//! low-level access as the libavcodec functions do.
use std::ffi::CStr;
use std::fmt::Debug;
use std::fmt::Display;
use std::marker::PhantomData;
use std::mem::ManuallyDrop;
use std::ops::Deref;
use libc::c_char;
use libc::c_int;
use libc::c_void;
use thiserror::Error as ThisError;
use super::*;
use crate::ffi::AVPictureType;
/// An error returned by a low-level libavcodec function.
#[derive(Debug, ThisError)]
pub struct AvError(pub libc::c_int);
impl AvError {
pub fn result(ret: c_int) -> Result<(), Self> {
if ret >= 0 {
Ok(())
} else {
Err(AvError(ret))
}
}
}
impl Display for AvError {
fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
let mut buffer = [0u8; 255];
let ret =
// SAFETY:
// Safe because we are passing valid bounds for the buffer.
unsafe { ffi::av_strerror(self.0, buffer.as_mut_ptr() as *mut c_char, buffer.len()) };
match ret {
ret if ret >= 0 => {
let end_of_string = buffer.iter().position(|i| *i == 0).unwrap_or(buffer.len());
let error_string = std::string::String::from_utf8_lossy(&buffer[..end_of_string]);
f.write_str(&error_string)
}
_ => f.write_fmt(format_args!("Unknown avcodec error {}", self.0)),
}
}
}
/// Lightweight abstraction over libavcodec's `AVCodec` struct, allowing the query the capabilities
/// of supported codecs and opening a session to work with them.
///
/// `AVCodec` instances in libavcodec are all static, hence we can safely use a static reference
/// lifetime here.
pub struct AvCodec(&'static ffi::AVCodec);
#[derive(Debug, ThisError)]
pub enum AvCodecOpenError {
#[error("failed to allocate AVContext object")]
ContextAllocation,
#[error("failed to open AVContext object")]
ContextOpen,
#[error("ContextBuilder variant does not match codec type")]
UnexpectedCodecType,
}
/// Dimensions of a frame, used in AvCodecContext and AvFrame.
#[derive(Copy, Clone, Debug, PartialEq, Eq)]
pub struct Dimensions {
pub width: u32,
pub height: u32,
}
impl AvCodec {
/// Returns whether the codec is a decoder.
pub fn is_decoder(&self) -> bool {
// SAFETY:
// Safe because `av_codec_is_decoder` is called on a valid static `AVCodec` reference.
(unsafe { ffi::av_codec_is_decoder(self.0) } != 0)
}
/// Returns whether the codec is an encoder.
pub fn is_encoder(&self) -> bool {
// SAFETY:
// Safe because `av_codec_is_encoder` is called on a valid static `AVCodec` reference.
(unsafe { ffi::av_codec_is_encoder(self.0) } != 0)
}
/// Returns the name of the codec.
pub fn name(&self) -> &'static str {
const INVALID_CODEC_STR: &str = "invalid codec";
// SAFETY:
// Safe because `CStr::from_ptr` is called on a valid zero-terminated C string.
unsafe { CStr::from_ptr(self.0.name).to_str() }.unwrap_or(INVALID_CODEC_STR)
}
/// Returns the capabilities of the codec, as a mask of AV_CODEC_CAP_* bits.
pub fn capabilities(&self) -> u32 {
self.0.capabilities as u32
}
/// Returns an iterator over the profiles supported by this codec.
pub fn profile_iter(&self) -> AvProfileIterator {
AvProfileIterator(self.0.profiles)
}
/// Returns an iterator over the pixel formats supported by this codec.
///
/// For a decoder, the returned array will likely be empty. This means that ffmpeg's native
/// pixel format (YUV420) will be used.
pub fn pixel_format_iter(&self) -> AvPixelFormatIterator {
AvPixelFormatIterator(self.0.pix_fmts)
}
/// Get a builder for a encoder [`AvCodecContext`] using this codec.
pub fn build_encoder(&self) -> Result<EncoderContextBuilder, AvCodecOpenError> {
if !self.is_encoder() {
return Err(AvCodecOpenError::UnexpectedCodecType);
}
Ok(EncoderContextBuilder {
codec: self.0,
context: self.alloc_context()?,
})
}
/// Get a builder for a decoder [`AvCodecContext`] using this codec.
pub fn build_decoder(&self) -> Result<DecoderContextBuilder, AvCodecOpenError> {
if !self.is_decoder() {
return Err(AvCodecOpenError::UnexpectedCodecType);
}
Ok(DecoderContextBuilder {
codec: self.0,
context: self.alloc_context()?,
})
}
/// Internal helper for `build_decoder` to allocate an [`AvCodecContext`]. This needs to be
/// paired with a later call to [`AvCodecContext::init`].
fn alloc_context(&self) -> Result<AvCodecContext, AvCodecOpenError> {
// TODO(b:315859322): add safety doc string
#[allow(clippy::undocumented_unsafe_blocks)]
let context = unsafe { ffi::avcodec_alloc_context3(self.0).as_mut() }
.ok_or(AvCodecOpenError::ContextAllocation)?;
Ok(AvCodecContext(context))
}
}
/// A builder to create a [`AvCodecContext`] suitable for decoding.
// This struct wraps an AvCodecContext directly, but the only way it can be taken out is to call
// `build()`, which finalizes the context and prevent further modification to the callback, etc.
pub struct DecoderContextBuilder {
codec: *const ffi::AVCodec,
context: AvCodecContext,
}
impl DecoderContextBuilder {
/// Set a custom callback that provides output buffers.
///
/// `get_buffer2` is a function that decides which buffer is used to render a frame (see
/// libavcodec's documentation for `get_buffer2` for more details). If provided, this function
/// must be thread-safe.
/// `opaque` is a pointer that will be passed as first argument to `get_buffer2` when it is
/// called.
pub fn set_get_buffer_2(
&mut self,
get_buffer2: unsafe extern "C" fn(*mut ffi::AVCodecContext, *mut ffi::AVFrame, i32) -> i32,
opaque: *mut libc::c_void,
) {
// SAFETY:
// Safe because self.context.0 is a pointer to a live AVCodecContext allocation.
let context = unsafe { &mut *(self.context.0) };
context.get_buffer2 = Some(get_buffer2);
context.opaque = opaque;
}
/// Build a decoder AvCodecContext from the configured options.
pub fn build(mut self) -> Result<AvCodecContext, AvCodecOpenError> {
self.context.init(self.codec)?;
Ok(self.context)
}
}
/// A builder to create a [`AvCodecContext`] suitable for encoding.
// This struct wraps an AvCodecContext directly, but the only way it can be taken out is to call
// `build()`, which finalizes the context and prevent further modification to the callback, etc.
pub struct EncoderContextBuilder {
codec: *const ffi::AVCodec,
context: AvCodecContext,
}
impl EncoderContextBuilder {
/// Set the width of input frames for this encoding context.
pub fn set_dimensions(&mut self, dimensions: Dimensions) {
// TODO(b:315859322): add safety doc string
#[allow(clippy::undocumented_unsafe_blocks)]
let context = unsafe { &mut *(self.context.0) };
context.width = dimensions.width as _;
context.height = dimensions.height as _;
}
/// Set the time base for this encoding context.
pub fn set_time_base(&mut self, time_base: ffi::AVRational) {
// TODO(b:315859322): add safety doc string
#[allow(clippy::undocumented_unsafe_blocks)]
let context = unsafe { &mut *(self.context.0) };
context.time_base = time_base;
}
/// Set the input pixel format for this encoding context.
pub fn set_pix_fmt(&mut self, fmt: AvPixelFormat) {
// TODO(b:315859322): add safety doc string
#[allow(clippy::undocumented_unsafe_blocks)]
let context = unsafe { &mut *(self.context.0) };
context.pix_fmt = fmt.pix_fmt();
}
/// Build a encoder AvCodecContext from the configured options.
pub fn build(mut self) -> Result<AvCodecContext, AvCodecOpenError> {
self.context.init(self.codec)?;
Ok(self.context)
}
}
impl Default for AvCodecIterator {
fn default() -> Self {
Self::new()
}
}
/// Lightweight abstraction over libavcodec's `av_codec_iterate` function that can be used to
/// enumerate all the supported codecs.
pub struct AvCodecIterator(*mut libc::c_void);
impl AvCodecIterator {
pub fn new() -> Self {
Self(std::ptr::null_mut())
}
}
impl Iterator for AvCodecIterator {
type Item = AvCodec;
fn next(&mut self) -> Option<Self::Item> {
// SAFETY:
// Safe because our pointer was initialized to `NULL` and we only use it with
// `av_codec_iterate`, which will update it to a valid value.
unsafe { ffi::av_codec_iterate(&mut self.0 as *mut *mut libc::c_void).as_ref() }
.map(AvCodec)
}
}
/// Simple wrapper over `AVProfile` that provides helpful methods.
pub struct AvProfile(&'static ffi::AVProfile);
impl AvProfile {
/// Return the profile id, which can be matched against FF_PROFILE_*.
pub fn profile(&self) -> u32 {
self.0.profile as u32
}
/// Return the name of this profile.
pub fn name(&self) -> &'static str {
const INVALID_PROFILE_STR: &str = "invalid profile";
// SAFETY:
// Safe because `CStr::from_ptr` is called on a valid zero-terminated C string.
unsafe { CStr::from_ptr(self.0.name).to_str() }.unwrap_or(INVALID_PROFILE_STR)
}
}
impl Display for AvProfile {
fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
f.write_str(self.name())
}
}
impl Debug for AvProfile {
fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
Display::fmt(self, f)
}
}
/// Lightweight abstraction over the array of supported profiles for a given codec.
pub struct AvProfileIterator(*const ffi::AVProfile);
impl Iterator for AvProfileIterator {
type Item = AvProfile;
fn next(&mut self) -> Option<Self::Item> {
// SAFETY:
// Safe because the contract of `new` stipulates we have received a valid `AVCodec`
// reference, thus the `profiles` pointer must either be NULL or point to a valid array
// or `VAProfile`s.
match unsafe { self.0.as_ref() } {
None => None,
Some(profile) => {
match profile.profile {
ffi::FF_PROFILE_UNKNOWN => None,
_ => {
// SAFETY:
// Safe because we have been initialized to a static, valid profiles array
// which is terminated by FF_PROFILE_UNKNOWN.
self.0 = unsafe { self.0.offset(1) };
Some(AvProfile(profile))
}
}
}
}
}
}
#[derive(Clone, Copy)]
/// Simple wrapper over `AVPixelFormat` that provides helpful methods.
pub struct AvPixelFormat(ffi::AVPixelFormat);
impl AvPixelFormat {
/// Return the name of this pixel format.
pub fn name(&self) -> &'static str {
const INVALID_FORMAT_STR: &str = "invalid pixel format";
// SAFETY:
// Safe because `av_get_pix_fmt_name` returns either NULL or a valid C string.
let pix_fmt_name = unsafe { ffi::av_get_pix_fmt_name(self.0) };
// SAFETY:
// Safe because `pix_fmt_name` is a valid pointer to a C string.
match unsafe {
pix_fmt_name
.as_ref()
.and_then(|s| CStr::from_ptr(s).to_str().ok())
} {
None => INVALID_FORMAT_STR,
Some(string) => string,
}
}
/// Return the avcodec profile id, which can be matched against AV_PIX_FMT_*.
///
/// Note that this is **not** the same as a fourcc.
pub fn pix_fmt(&self) -> ffi::AVPixelFormat {
self.0
}
/// Return the fourcc of the pixel format, or a series of zeros if its fourcc is unknown.
pub fn fourcc(&self) -> [u8; 4] {
// SAFETY:
// Safe because `avcodec_pix_fmt_to_codec_tag` does not take any pointer as input and
// handles any value passed as argument.
unsafe { ffi::avcodec_pix_fmt_to_codec_tag(self.0) }.to_le_bytes()
}
/// Given the width and plane index, returns the line size (data pointer increment per row) in
/// bytes.
pub fn line_size(&self, width: u32, plane: usize) -> Result<usize, AvError> {
av_image_line_size(*self, width, plane)
}
/// Given an iterator of line sizes and height, return the size required for each plane's buffer
/// in bytes.
pub fn plane_sizes<I: IntoIterator<Item = u32>>(
&self,
linesizes: I,
height: u32,
) -> Result<Vec<usize>, AvError> {
av_image_plane_sizes(*self, linesizes, height)
}
}
#[derive(Debug)]
pub struct FromAVPixelFormatError(());
impl TryFrom<ffi::AVPixelFormat> for AvPixelFormat {
type Error = FromAVPixelFormatError;
fn try_from(value: ffi::AVPixelFormat) -> Result<Self, Self::Error> {
if value > ffi::AVPixelFormat_AV_PIX_FMT_NONE && value < ffi::AVPixelFormat_AV_PIX_FMT_NB {
Ok(AvPixelFormat(value))
} else {
Err(FromAVPixelFormatError(()))
}
}
}
impl Display for AvPixelFormat {
fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
f.write_str(self.name())
}
}
impl Debug for AvPixelFormat {
fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
let fourcc = self.fourcc();
f.write_fmt(format_args!(
"{}{}{}{}",
fourcc[0] as char, fourcc[1] as char, fourcc[2] as char, fourcc[3] as char
))
}
}
/// Lightweight abstraction over the array of supported pixel formats for a given codec.
pub struct AvPixelFormatIterator(*const ffi::AVPixelFormat);
impl Iterator for AvPixelFormatIterator {
type Item = AvPixelFormat;
fn next(&mut self) -> Option<Self::Item> {
// SAFETY:
// Safe because the contract of `AvCodec::new` and `AvCodec::pixel_format_iter` guarantees
// that we have been built from a valid `AVCodec` reference, which `pix_fmts` pointer
// must either be NULL or point to a valid array or `VAPixelFormat`s.
match unsafe { self.0.as_ref() } {
None => None,
Some(&pixfmt) => {
match pixfmt {
// Array of pixel formats is terminated by AV_PIX_FMT_NONE.
ffi::AVPixelFormat_AV_PIX_FMT_NONE => None,
_ => {
// SAFETY:
// Safe because we have been initialized to a static, valid profiles array
// which is terminated by AV_PIX_FMT_NONE.
self.0 = unsafe { self.0.offset(1) };
Some(AvPixelFormat(pixfmt))
}
}
}
}
}
}
/// A codec context from which decoding can be performed.
pub struct AvCodecContext(*mut ffi::AVCodecContext);
impl Drop for AvCodecContext {
fn drop(&mut self) {
// SAFETY:
// Safe because our context member is properly allocated and owned by us.
// Note: `avcodec_open2` might not have been called in case we're wrapped by a
// `DecoderContextBuilder` but avcodec_free_context works on both opened and closed
// contexts.
unsafe { ffi::avcodec_free_context(&mut self.0) };
}
}
impl AsRef<ffi::AVCodecContext> for AvCodecContext {
fn as_ref(&self) -> &ffi::AVCodecContext {
// SAFETY:
// Safe because our context member is properly initialized and fully owned by us.
unsafe { &*self.0 }
}
}
pub enum TryReceiveResult {
Received,
TryAgain,
FlushCompleted,
}
impl AvCodecContext {
/// Internal helper for [`DecoderContextBuilder`] to initialize the context.
fn init(&mut self, codec: *const ffi::AVCodec) -> Result<(), AvCodecOpenError> {
// SAFETY:
// Safe because `codec` is a valid static AVCodec reference, and `self.0` is a valid
// AVCodecContext allocation.
if unsafe { ffi::avcodec_open2(self.0, codec, std::ptr::null_mut()) } < 0 {
return Err(AvCodecOpenError::ContextOpen);
}
Ok(())
}
/// Send a packet to be decoded by the codec.
///
/// Returns `true` if the packet has been accepted and will be decoded, `false` if the codec can
/// not accept frames at the moment - in this case `try_receive_frame` must be called before
/// the packet can be submitted again.
///
/// Error codes are the same as those returned by `avcodec_send_packet` with the exception of
/// EAGAIN which is converted into `Ok(false)` as it is not actually an error.
pub fn try_send_packet(&mut self, packet: &AvPacket) -> Result<bool, AvError> {
// SAFETY:
// Safe because the context is valid through the life of this object, and `packet`'s
// lifetime properties ensures its memory area is readable.
match unsafe { ffi::avcodec_send_packet(self.0, &packet.packet) } {
AVERROR_EAGAIN => Ok(false),
ret if ret >= 0 => Ok(true),
err => Err(AvError(err)),
}
}
/// Attempt to write a decoded frame in `frame` if the codec has enough data to do so.
///
/// Returned `Received` if `frame` has been filled with the next decoded frame, `TryAgain` if
/// no frame could be returned at that time (in which case `try_send_packet` should be called to
/// submit more input to decode), or `FlushCompleted` to signal that a previous flush triggered
/// by calling the `flush` method has completed.
///
/// Error codes are the same as those returned by `avcodec_receive_frame` with the exception of
/// EAGAIN and EOF which are handled as `TryAgain` and `FlushCompleted` respectively.
pub fn try_receive_frame(&mut self, frame: &mut AvFrame) -> Result<TryReceiveResult, AvError> {
// SAFETY:
// Safe because the context is valid through the life of this object, and `avframe` is
// guaranteed to contain a properly initialized frame.
match unsafe { ffi::avcodec_receive_frame(self.0, frame.0) } {
AVERROR_EAGAIN => Ok(TryReceiveResult::TryAgain),
AVERROR_EOF => Ok(TryReceiveResult::FlushCompleted),
ret if ret >= 0 => Ok(TryReceiveResult::Received),
err => Err(AvError(err)),
}
}
/// Send a frame to be encoded by the codec.
///
/// Returns `true` if the frame has been accepted and will be encoded, `false` if the codec can
/// not accept input at the moment - in this case `try_receive_frame` must be called before
/// the frame can be submitted again.
///
/// Error codes are the same as those returned by `avcodec_send_frame` with the exception of
/// EAGAIN which is converted into `Ok(false)` as it is not actually an error.
pub fn try_send_frame(&mut self, frame: &AvFrame) -> Result<bool, AvError> {
// TODO(b:315859322): add safety doc string
#[allow(clippy::undocumented_unsafe_blocks)]
match unsafe { ffi::avcodec_send_frame(self.0, frame.0 as *const _) } {
AVERROR_EAGAIN => Ok(false),
ret if ret >= 0 => Ok(true),
err => Err(AvError(err)),
}
}
/// Attempt to write an encoded frame in `packet` if the codec has enough data to do so.
///
/// Returned `Received` if `packet` has been filled with encoded data, `TryAgain` if
/// no packet could be returned at that time (in which case `try_send_frame` should be called to
/// submit more input to decode), or `FlushCompleted` to signal that a previous flush triggered
/// by calling the `flush` method has completed.
///
/// Error codes are the same as those returned by `avcodec_receive_packet` with the exception of
/// EAGAIN and EOF which are handled as `TryAgain` and `FlushCompleted` respectively.
pub fn try_receive_packet(
&mut self,
packet: &mut AvPacket,
) -> Result<TryReceiveResult, AvError> {
// SAFETY:
// Safe because the context is valid through the life of this object, and `avframe` is
// guaranteed to contain a properly initialized frame.
match unsafe { ffi::avcodec_receive_packet(self.0, &mut packet.packet) } {
AVERROR_EAGAIN => Ok(TryReceiveResult::TryAgain),
AVERROR_EOF => Ok(TryReceiveResult::FlushCompleted),
ret if ret >= 0 => Ok(TryReceiveResult::Received),
err => Err(AvError(err)),
}
}
/// Reset the internal codec state/flush internal buffers.
/// Should be called e.g. when seeking or switching to a different stream.
pub fn reset(&mut self) {
// SAFETY:
// Safe because the context is valid through the life of this object.
unsafe { ffi::avcodec_flush_buffers(self.0) }
}
/// Ask the context to start flushing, i.e. to process all pending input packets and produce
/// frames for them.
///
/// The flush process is complete when `try_receive_frame` returns `FlushCompleted`,
pub fn flush_decoder(&mut self) -> Result<(), AvError> {
// SAFETY:
// Safe because the context is valid through the life of this object.
AvError::result(unsafe { ffi::avcodec_send_packet(self.0, std::ptr::null()) })
}
/// Ask the context to start flushing, i.e. to process all pending input frames and produce
/// packets for them.
///
/// The flush process is complete when `try_receive_packet` returns `FlushCompleted`,
pub fn flush_encoder(&mut self) -> Result<(), AvError> {
// SAFETY:
// Safe because the context is valid through the life of this object.
AvError::result(unsafe { ffi::avcodec_send_frame(self.0, std::ptr::null()) })
}
/// Set the time base for this context.
pub fn set_time_base(&mut self, time_base: AVRational) {
// TODO(b:315859322): add safety doc string
#[allow(clippy::undocumented_unsafe_blocks)]
let context = unsafe { &mut *(self.0) };
context.time_base = time_base;
}
/// Set the bit rate for this context.
pub fn set_bit_rate(&mut self, bit_rate: u64) {
// TODO(b:315859322): add safety doc string
#[allow(clippy::undocumented_unsafe_blocks)]
let context = unsafe { &mut *(self.0) };
context.bit_rate = bit_rate as _;
}
/// Set the max bit rate (rc_max_rate) for this context.
pub fn set_max_bit_rate(&mut self, bit_rate: u64) {
// TODO(b:315859322): add safety doc string
#[allow(clippy::undocumented_unsafe_blocks)]
let context = unsafe { &mut *(self.0) };
context.rc_max_rate = bit_rate as _;
}
}
/// Trait for types that can be used as data provider for a `AVBuffer`.
///
/// `AVBuffer` is an owned buffer type, so all the type needs to do is being able to provide a
/// stable pointer to its own data as well as its length. Implementors need to be sendable across
/// threads because avcodec is allowed to use threads in its codec implementations.
pub trait AvBufferSource: Send {
fn as_ptr(&self) -> *const u8;
fn as_mut_ptr(&mut self) -> *mut u8 {
self.as_ptr() as *mut u8
}
fn len(&self) -> usize;
fn is_empty(&self) -> bool;
}
/// Wrapper around `AVBuffer` and `AVBufferRef`.
///
/// libavcodec can manage its own memory for input and output data. Doing so implies a transparent
/// copy of user-provided data (packets or frames) from and to this memory, which is wasteful.
///
/// This copy can be avoided by explicitly providing our own buffers to libavcodec using
/// `AVBufferRef`. Doing so means that the lifetime of these buffers becomes managed by avcodec.
/// This struct helps make this process safe by taking full ownership of an `AvBufferSource` and
/// dropping it when libavcodec is done with it.
pub struct AvBuffer(*mut ffi::AVBufferRef);
impl AvBuffer {
/// Create a new `AvBuffer` from an `AvBufferSource`.
///
/// Ownership of `source` is transferred to libavcodec, which will drop it when the number of
/// references to this buffer reaches zero.
///
/// Returns `None` if the buffer could not be created due to an error in libavcodec.
pub fn new<D: AvBufferSource + 'static>(source: D) -> Option<Self> {
// Move storage to the heap so we find it at the same place in `avbuffer_free`
let mut storage = Box::new(source);
extern "C" fn avbuffer_free<D>(opaque: *mut c_void, _data: *mut u8) {
// SAFETY:
// Safe because `opaque` has been created from `Box::into_raw`. `storage` will be
// dropped immediately which will release any resources held by the storage.
let _ = unsafe { Box::from_raw(opaque as *mut D) };
}
// SAFETY:
// Safe because storage points to valid data throughout the lifetime of AVBuffer and we are
// checking the return value against NULL, which signals an error.
Some(Self(unsafe {
ffi::av_buffer_create(
storage.as_mut_ptr(),
storage.len(),
Some(avbuffer_free::<D>),
Box::into_raw(storage) as *mut c_void,
0,
)
.as_mut()?
}))
}
/// Return a slice to the data contained in this buffer.
pub fn as_mut_slice(&mut self) -> &mut [u8] {
// SAFETY:
// Safe because the data has been initialized from valid storage in the constructor.
unsafe { std::slice::from_raw_parts_mut((*self.0).data, (*self.0).size) }
}
/// Consumes the `AVBuffer`, returning a `AVBufferRef` that can be used in `AVFrame`, `AVPacket`
/// and others.
///
/// After calling, the caller is responsible for unref-ing the returned AVBufferRef, either
/// directly or through one of the automatic management facilities in `AVFrame`, `AVPacket` or
/// others.
pub fn into_raw(self) -> *mut ffi::AVBufferRef {
ManuallyDrop::new(self).0
}
}
impl Drop for AvBuffer {
fn drop(&mut self) {
// SAFETY:
// Safe because `self.0` is a valid pointer to an AVBufferRef.
unsafe { ffi::av_buffer_unref(&mut self.0) };
}
}
/// An encoded input packet that can be submitted to `AvCodecContext::try_send_packet`.
pub struct AvPacket<'a> {
packet: ffi::AVPacket,
_buffer_data: PhantomData<&'a ()>,
}
impl<'a> Drop for AvPacket<'a> {
fn drop(&mut self) {
// SAFETY:
// Safe because `self.packet` is a valid `AVPacket` instance.
unsafe {
ffi::av_packet_unref(&mut self.packet);
}
}
}
impl<'a> AsRef<ffi::AVPacket> for AvPacket<'a> {
fn as_ref(&self) -> &ffi::AVPacket {
&self.packet
}
}
impl<'a> AvPacket<'a> {
/// Create an empty AvPacket without buffers.
///
/// This packet should be only used with an encoder; in which case the encoder will
/// automatically allocate a buffer of appropriate size and store it inside this `AvPacket`.
pub fn empty() -> Self {
Self {
packet: ffi::AVPacket {
pts: AV_NOPTS_VALUE as i64,
dts: AV_NOPTS_VALUE as i64,
pos: -1,
// SAFETY:
// Safe because all the other elements of this struct can be zeroed.
..unsafe { std::mem::zeroed() }
},
_buffer_data: PhantomData,
}
}
/// Create a new AvPacket that borrows the `input_data`.
///
/// The returned `AvPacket` will hold a reference to `input_data`, meaning that libavcodec might
/// perform a copy from/to it.
pub fn new<T: AvBufferSource>(pts: i64, input_data: &'a mut T) -> Self {
Self {
packet: ffi::AVPacket {
buf: std::ptr::null_mut(),
pts,
dts: AV_NOPTS_VALUE as i64,
data: input_data.as_mut_ptr(),
size: input_data.len() as c_int,
side_data: std::ptr::null_mut(),
pos: -1,
// SAFETY:
// Safe because all the other elements of this struct can be zeroed.
..unsafe { std::mem::zeroed() }
},
_buffer_data: PhantomData,
}
}
/// Create a new AvPacket that owns the `av_buffer`.
///
/// The returned `AvPacket` will have a `'static` lifetime and will keep `input_data` alive for
/// as long as libavcodec needs it.
pub fn new_owned(pts: i64, mut av_buffer: AvBuffer) -> Self {
let data_slice = av_buffer.as_mut_slice();
let data = data_slice.as_mut_ptr();
let size = data_slice.len() as i32;
Self {
packet: ffi::AVPacket {
buf: av_buffer.into_raw(),
pts,
dts: AV_NOPTS_VALUE as i64,
data,
size,
side_data: std::ptr::null_mut(),
pos: -1,
// SAFETY:
// Safe because all the other elements of this struct can be zeroed.
..unsafe { std::mem::zeroed() }
},
_buffer_data: PhantomData,
}
}
}
/// An owned AVFrame, i.e. one decoded frame from libavcodec that can be converted into a
/// destination buffer.
pub struct AvFrame(*mut ffi::AVFrame);
/// A builder for AVFrame that allows specifying buffers and image metadata.
pub struct AvFrameBuilder(AvFrame);
/// A descriptor describing a subslice of `buffers` in [`AvFrameBuilder::build_owned`] that
/// represents a plane's image data.
pub struct PlaneDescriptor {
/// The index within `buffers`.
pub buffer_index: usize,
/// The offset from the start of `buffers[buffer_index]`.
pub offset: usize,
/// The increment of data pointer in bytes per row of the plane.
pub stride: usize,
}
#[derive(Debug, ThisError)]
pub enum AvFrameError {
#[error("failed to allocate AVFrame object")]
FrameAllocationFailed,
#[error("dimension is negative or too large")]
DimensionOverflow,
#[error("a row does not fit in the specified stride")]
InvalidStride,
#[error("buffer index out of range")]
BufferOutOfRange,
#[error("specified dimensions overflow the buffer size")]
BufferTooSmall,
#[error("plane reference to buffer alias each other")]
BufferAlias,
#[error("error while calling libavcodec")]
AvError(#[from] AvError),
}
impl AvFrame {
/// Create a new AvFrame. The frame's parameters and backing memory will be assigned when it is
/// decoded into.
pub fn new() -> Result<Self, AvFrameError> {
Ok(Self(
// SAFETY:
// Safe because `av_frame_alloc` does not take any input.
unsafe { ffi::av_frame_alloc().as_mut() }.ok_or(AvFrameError::FrameAllocationFailed)?,
))
}
/// Create a new AvFrame builder that allows setting the frame's parameters and backing memory
/// through its methods.
pub fn builder() -> Result<AvFrameBuilder, AvFrameError> {
AvFrame::new().map(AvFrameBuilder)
}
/// Return the frame's width and height.
pub fn dimensions(&self) -> Dimensions {
Dimensions {
width: self.as_ref().width as _,
height: self.as_ref().height as _,
}
}
/// Return the frame's pixel format.
pub fn format(&self) -> AvPixelFormat {
AvPixelFormat(self.as_ref().format)
}
/// Set the picture type (I-frame, P-frame etc.) on this frame.
pub fn set_pict_type(&mut self, ty: AVPictureType) {
// SAFETY:
// Safe because self.0 is a valid AVFrame reference.
unsafe {
(*self.0).pict_type = ty;
}
}
/// Set the presentation timestamp (PTS) of this frame.
pub fn set_pts(&mut self, ts: i64) {
// SAFETY:
// Safe because self.0 is a valid AVFrame reference.
unsafe {
(*self.0).pts = ts;
}
}
/// Query if this AvFrame is writable, i.e. it is refcounted and the refcounts are 1.
pub fn is_writable(&self) -> bool {
// SAFETY:
// Safe because self.0 is a valid AVFrame reference.
unsafe { ffi::av_frame_is_writable(self.0) != 0 }
}
/// If the frame is not writable already (see [`is_writable`]), make a copy of its buffer to
/// make it writable.
///
/// [`is_writable`]: AvFrame::is_writable
pub fn make_writable(&mut self) -> Result<(), AvFrameError> {
// SAFETY:
// Safe because self.0 is a valid AVFrame reference.
AvError::result(unsafe { ffi::av_frame_make_writable(self.0) }).map_err(Into::into)
}
}
impl AvFrameBuilder {
/// Set the frame's width and height.
///
/// The dimensions must not be greater than `i32::MAX`.
pub fn set_dimensions(&mut self, dimensions: Dimensions) -> Result<(), AvFrameError> {
// SAFETY:
// Safe because self.0 is a valid AVFrame instance and width and height are in range.
unsafe {
(*self.0 .0).width = dimensions
.width
.try_into()
.map_err(|_| AvFrameError::DimensionOverflow)?;
(*self.0 .0).height = dimensions
.height
.try_into()
.map_err(|_| AvFrameError::DimensionOverflow)?;
}
Ok(())
}
/// Set the frame's format.
pub fn set_format(&mut self, format: AvPixelFormat) -> Result<(), AvFrameError> {
// SAFETY:
// Safe because self.0 is a valid AVFrame instance and format is a valid pixel format.
unsafe {
(*self.0 .0).format = format.pix_fmt();
}
Ok(())
}
/// Build an AvFrame from iterators of [`AvBuffer`]s and subslice of buffers describing the
/// planes.
///
/// The frame will own the `buffers`.
///
/// This function checks that:
/// - Each plane fits inside the bounds of the associated buffer.
/// - Different planes do not overlap each other's buffer slice. In this check, all planes are
/// assumed to be potentially mutable, regardless of whether the AvFrame is actually used for
/// read or write access. Aliasing reference to the same buffer will be rejected, since it can
/// potentially allow routines to overwrite each
// other's result.
/// An exception to this is when the same buffer is passed multiple times in `buffers`. In
/// this case, each buffer is treated as a different buffer. Since clones have to be made to
/// be passed multiple times in `buffers`, the frame will not be considered [writable]. Hence
/// aliasing is safe in this case, but the caller is required to explicit opt-in to this
/// read-only handling by passing clones of the buffer into `buffers` and have a different
/// buffer index for each plane combination that could overlap in their range.
///
/// [writable]: AvFrame::is_writable
pub fn build_owned<
BI: IntoIterator<Item = AvBuffer>,
PI: IntoIterator<Item = PlaneDescriptor>,
>(
self,
buffers: BI,
planes: PI,
) -> Result<AvFrame, AvFrameError> {
let mut buffers: Vec<_> = buffers.into_iter().collect();
let planes: Vec<_> = planes.into_iter().collect();
let format = self.0.format();
let plane_sizes = format.plane_sizes(
planes.iter().map(|x| x.stride as u32),
self.0.dimensions().height,
)?;
let mut ranges = vec![];
for (
plane,
PlaneDescriptor {
buffer_index,
offset,
stride,
},
) in planes.into_iter().enumerate()
{
if buffer_index > buffers.len() {
return Err(AvFrameError::BufferOutOfRange);
}
let end = offset + plane_sizes[plane];
if end > buffers[buffer_index].as_mut_slice().len() {
return Err(AvFrameError::BufferTooSmall);
}
if stride < format.line_size(self.0.dimensions().width, plane)? {
return Err(AvFrameError::InvalidStride);
}
// TODO(b:315859322): add safety doc string
#[allow(clippy::undocumented_unsafe_blocks)]
unsafe {
(*self.0 .0).data[plane] =
buffers[buffer_index].as_mut_slice()[offset..].as_mut_ptr();
(*self.0 .0).linesize[plane] = stride as c_int;
}
ranges.push((buffer_index, offset, end));
}
// Check for range overlaps.
// See function documentation for the exact rule and reasoning.
ranges.sort_unstable();
for pair in ranges.windows(2) {
// (buffer_index, start, end)
let (b0, _s0, e0) = pair[0];
let (b1, s1, _e1) = pair[1];
if b0 != b1 {
continue;
}
// Note that s0 <= s1 always holds, so we only need to check
// that the start of the second range is before the end of the first range.
if s1 < e0 {
return Err(AvFrameError::BufferAlias);
}
}
for (i, buf) in buffers.into_iter().enumerate() {
// SAFETY:
// Safe because self.0 is a valid AVFrame instance and buffers contains valid AvBuffers.
unsafe {
(*self.0 .0).buf[i] = buf.into_raw();
}
}
Ok(self.0)
}
}
impl AsRef<ffi::AVFrame> for AvFrame {
fn as_ref(&self) -> &ffi::AVFrame {
// SAFETY:
// Safe because the AVFrame has been properly initialized during construction.
unsafe { &*self.0 }
}
}
impl Deref for AvFrame {
type Target = ffi::AVFrame;
fn deref(&self) -> &Self::Target {
// SAFETY:
// Safe because the AVFrame has been properly initialized during construction.
unsafe { self.0.as_ref().unwrap() }
}
}
impl Drop for AvFrame {
fn drop(&mut self) {
// SAFETY:
// Safe because the AVFrame is valid through the life of this object and fully owned by us.
unsafe { ffi::av_frame_free(&mut self.0) };
}
}
#[cfg(test)]
mod tests {
use std::sync::atomic::AtomicBool;
use std::sync::atomic::Ordering;
use std::sync::Arc;
use super::*;
#[test]
fn test_averror() {
// Just test that the error is wrapper properly. The bindings test module already checks
// that the error bindings correspond to the right ffmpeg errors.
let averror = AvError(AVERROR_EOF);
let msg = format!("{}", averror);
assert_eq!(msg, "End of file");
let averror = AvError(0);
let msg = format!("{}", averror);
assert_eq!(msg, "Success");
let averror = AvError(10);
let msg = format!("{}", averror);
assert_eq!(msg, "Unknown avcodec error 10");
}
// Test that the AVPacket wrapper frees the owned AVBuffer on drop.
#[test]
fn test_avpacket_drop() {
struct DropTestBufferSource {
dropped: Arc<AtomicBool>,
}
impl Drop for DropTestBufferSource {
fn drop(&mut self) {
self.dropped.store(true, Ordering::SeqCst);
}
}
impl AvBufferSource for DropTestBufferSource {
fn as_ptr(&self) -> *const u8 {
[].as_ptr()
}
fn len(&self) -> usize {
0
}
fn is_empty(&self) -> bool {
true
}
}
let dropped = Arc::new(AtomicBool::new(false));
let pkt = AvPacket::new_owned(
0,
AvBuffer::new(DropTestBufferSource {
dropped: dropped.clone(),
})
.unwrap(),
);
assert!(!dropped.load(Ordering::SeqCst));
drop(pkt);
assert!(dropped.load(Ordering::SeqCst));
}
}