使用C＃从flv文件中提取信息

Question

是否有代码帮助使用C＃从flv文件中提取头部信息和目标帧？

Answer 1

也许this article可以帮到你。它展示了如何在c＃中读取flv文件及其元信息。

基本上，您必须打开二进制文件流并读取文件的第一部分。

您必须解释根据Adobe flv format specification读取的字节数。 无论如何，本文有一些代码示例向您展示如何读取所有标头信息。

Answer 2

Library for FLV/F4V conversation in C# .NET?

其中一个图书馆可能对您有所帮助。

Answer 3

在尝试使用可接受的答案代码时，我最终还是这样做了

using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

/// <summary>
/// 
/// mauriciogracia@gmail.com
/// 
/// </summary>
namespace VideoUtils.Impl
{

    /// <summary>
    /// Reads the meta information embedded in an FLV byte stream 
    /// </summary>

    public class MetaDataStreamReader
    {


        /// <summary>
        /// Reads the meta information (if present) in an FLV
        /// </summary>
        /// <param name="path">The path to the FLV file</returns>
        public static VideoMetaData GetMetaDataInfo(MemoryStream memStream, string location)
        {
            bool hasMetaData = false;
            double duration = 0;
            double width = 0;
            double height = 0;
            double videoDataRate = 0;
            double audioDataRate = 0;
            Double frameRate = 0;
            DateTime creationDate = DateTime.MinValue;

            if(memStream == null)
            {
                throw new ArgumentNullException("Parameter MemoryStream is null");
            }

            try
            {
                // read where "onMetaData"
                byte[] bytes = new byte[10];
                memStream.Seek(27, SeekOrigin.Begin);
                int result = memStream.Read(bytes, 0, 10);
                // if "onMetaData" exists then proceed to read the attributes
                string onMetaData = ByteArrayToString(bytes);

                if (onMetaData == "onMetaData")
                {
                    hasMetaData = true;
                    // 16 bytes past "onMetaData" is the data for "duration" 
                    duration = GetNextDouble(memStream, 16, 8);
                    // 8 bytes past "duration" is the data for "width"
                    width = GetNextDouble(memStream, 8, 8);
                    // 9 bytes past "width" is the data for "height"
                    height = GetNextDouble(memStream, 9, 8);
                    // 16 bytes past "height" is the data for "videoDataRate"
                    videoDataRate = GetNextDouble(memStream, 16, 8);
                    // 16 bytes past "videoDataRate" is the data for "audioDataRate"
                    audioDataRate = GetNextDouble(memStream, 16, 8);
                    // 12 bytes past "audioDataRate" is the data for "frameRate"
                    frameRate = GetNextDouble(memStream, 12, 8);
                    // read in bytes for creationDate manually
                    memStream.Seek(17, SeekOrigin.Current);
                    byte[] seekBytes = new byte[24];
                    result = memStream.Read(seekBytes, 0, 24);

                    /*
                    string dateString = ByteArrayToString(seekBytes);
                    // create .NET readable date string
                    // cut off Day of Week
                    dateString = dateString.Substring(4);
                    // grab 1) month and day, 2) year, 3) time
                    dateString = dateString.Substring(0, 6) + " " + dateString.Substring(16, 4) + " " + dateString.Substring(7, 8);
                    // .NET 2.0 has DateTime.TryParse
                    try
                    {
                        creationDate = Convert.ToDateTime(dateString);
                    }
                    catch { }
                    */
                }
            }
            catch (Exception )
            {
                // no error handling
            }
            finally
            {
                if (memStream != null)
                {
                    memStream.Close();
                }
            }

            return  VideoMetaData.CreateFlvMetaInfo(hasMetaData, duration, width, height, videoDataRate, audioDataRate, frameRate, creationDate, location);
        }
        private static Double GetNextDouble(MemoryStream memStream, int offset, int length)
        {
            // move the desired number of places in the array
            memStream.Seek(offset, SeekOrigin.Current);

            // create byte array
            byte[] bytes = new byte[length];

            // read bytes
            int result = memStream.Read(bytes, 0, length);

            // convert to double (all flass values are written in reverse order)
            return ByteArrayToDouble(bytes, true);
        }
        private static string ByteArrayToString(byte[] bytes)
        {
            string byteString = string.Empty;
            foreach (byte b in bytes)
            {
                byteString += Convert.ToChar(b).ToString();
            }
            return byteString;
        }
        private static Double ByteArrayToDouble(byte[] bytes, bool readInReverse)
        {
            if (bytes.Length != 8)
                throw new Exception("bytes must be exactly 8 in Length");
            if (readInReverse)
                Array.Reverse(bytes);
            return BitConverter.ToDouble(bytes, 0);
        }
    }
}