Free online ISMV to FLAC converter

What the ISMV format is

ISMV, or Ismv Smooth Streaming video, is a fragmented MP4-based media format used for adaptive streaming. It commonly contains H.264 video and AAC audio divided into segments that a streaming server can deliver at different bitrates.

Microsoft Expression Encoder, IIS Media Services Smooth Streaming publishing tools, and some Azure Media Services workflows create ISMV files. You may encounter them in a server-side streaming package, a downloaded media archive, or an application that saved individual Smooth Streaming segments. An ISMV file may contain video, one or more audio tracks, subtitles, or only a subset of the original presentation.

What the FLAC format is

FLAC is a lossless audio codec stored in a format supported by music players, audio editors, media servers, and archival software. It reduces PCM audio size without discarding samples and preserves the decoded source exactly when the source itself is lossless.

FLAC is useful when you need an audio-only file for editing, tagging, long-term storage, or playback on software that does not support ISMV. It usually produces larger files than AAC or MP3 because it preserves all decoded audio data; it cannot recover quality already removed by a lossy source codec.

How to convert ISMV to FLAC

FFmpeg is the most practical desktop tool because it can read fragmented MP4 media and select the audio stream without first exporting the video.

1. Install a current FFmpeg build and place the ISMV file in an accessible folder.
2. Check the streams with ffprobe input.ismv. Look for an audio stream and note its codec, sample rate, channel count, and stream index.
3. Extract the first audio stream and encode it as FLAC:

ffmpeg -i input.ismv -map 0:a:0 -c:a flac output.flac

The option -map 0:a:0 selects the first audio stream and prevents video or unrelated data from being included. Replace input.ismv and output.flac with the actual filenames.

For a second audio stream, use -map 0:a:1. Since one FLAC file normally represents one audio stream, run a separate command for each track:

ffmpeg -i input.ismv -map 0:a:1 -c:a flac alternate.flac

To preserve common metadata where FFmpeg can read it, add -map_metadata 0:

ffmpeg -i input.ismv -map 0:a:0 -map_metadata 0 -c:a flac output.flac

On Windows, quote paths containing spaces, for example ffmpeg -i "C:\Media\segment.ismv" -map 0:a:0 -c:a flac "C:\Music\segment.flac". On macOS or Linux, quote paths with spaces using single or double quotation marks.

If you prefer not to install software, the built-in converter on 101convert.com can convert the file online for free. Uploading may be unsuitable for confidential media or large files, and the service must be able to recognize an audio stream inside the ISMV container.

Quality, compatibility, and limitations

FLAC encoding is lossless only relative to the decoded input. If the ISMV contains AAC, the conversion removes the AAC wrapper but does not restore information discarded during AAC compression; the FLAC file will retain the quality of the AAC decode, not the quality of an original master.

An ISMV containing no audio stream cannot produce a meaningful FLAC file. If FFmpeg reports only video streams, check whether another segment or source file contains the audio.

Do not use stream copying for this conversion: -c:a copy copies the original codec and will not create FLAC. The -c:a flac encoder must decode the source and re-encode the resulting PCM audio.

FLAC supports common sample rates, channel layouts, and bit depths, but compatibility can improve if a target application requires a specific layout. For example, convert to stereo 16-bit FLAC with ffmpeg -i input.ismv -map 0:a:0 -c:a flac -ac 2 -sample_fmt s16 output.flac. This changes the channel arrangement or precision when necessary, so omit those options when preserving the decoded source format is preferred.