From 5b36faa08d0d6ec8543877186521e1912ca2bbbd Mon Sep 17 00:00:00 2001
From: Arrizal Amin <arrizalamin@gmail.com>
Date: Sat, 3 Aug 2024 13:45:06 +0700
Subject: [PATCH] add frame-specific seek method

---
 src/decode.rs | 18 ++++++++++++++++--
 src/io.rs     | 15 +++++++++++++++
 2 files changed, 31 insertions(+), 2 deletions(-)

diff --git a/src/decode.rs b/src/decode.rs
index 52b135f..4fe51c2 100644
--- a/src/decode.rs
+++ b/src/decode.rs
@@ -224,7 +224,19 @@ impl Decoder {
     /// See [`Reader::seek`](crate::io::Reader::seek) for more information.
     #[inline]
     pub fn seek(&mut self, timestamp_milliseconds: i64) -> Result<()> {
-        self.reader.seek(timestamp_milliseconds)
+        self.reader
+            .seek(timestamp_milliseconds)
+            .inspect(|_| self.decoder.decoder.flush())
+    }
+
+    /// Seek to specific frame in reader.
+    ///
+    /// See [`Reader::seek_to_frame`](crate::io::Reader::seek_to_frame) for more information.
+    #[inline]
+    pub fn seek_to_frame(&mut self, frame_number: i64) -> Result<()> {
+        self.reader
+            .seek_to_frame(frame_number)
+            .inspect(|_| self.decoder.decoder.flush())
     }
 
     /// Seek to start of reader.
@@ -232,7 +244,9 @@ impl Decoder {
     /// See [`Reader::seek_to_start`](crate::io::Reader::seek_to_start) for more information.
     #[inline]
     pub fn seek_to_start(&mut self) -> Result<()> {
-        self.reader.seek_to_start()
+        self.reader
+            .seek_to_start()
+            .inspect(|_| self.decoder.decoder.flush())
     }
 
     /// Split the decoder into a decoder (of type [`DecoderSplit`]) and a [`Reader`].
diff --git a/src/io.rs b/src/io.rs
index fc0a47e..0c730a0 100644
--- a/src/io.rs
+++ b/src/io.rs
@@ -5,6 +5,7 @@ use ffmpeg::ffi::AV_TIME_BASE_Q;
 use ffmpeg::format::context::{Input as AvInput, Output as AvOutput};
 use ffmpeg::media::Type as AvMediaType;
 use ffmpeg::Error as AvError;
+use ffmpeg_next::ffi::av_seek_frame;
 
 use crate::error::Error;
 use crate::ffi;
@@ -157,6 +158,20 @@ impl Reader {
             .map_err(Error::BackendError)
     }
 
+    /// Seek to a specific frame in the video stream.
+    ///
+    /// # Arguments
+    ///
+    /// * `frame_number` - The frame number to seek to.
+    pub fn seek_to_frame(&mut self, frame_number: i64) -> Result<()> {
+        unsafe {
+            match av_seek_frame(self.input.as_mut_ptr(), -1, frame_number, 0) {
+                0 => Ok(()),
+                e => Err(Error::BackendError(AvError::from(e))),
+            }
+        }
+    }
+
     /// Seek to start of reader. This function performs best effort seeking to the start of the
     /// file.
     pub fn seek_to_start(&mut self) -> Result<()> {