FLV to AVCHD Converter

Convert FLV to AVCHD: What This Tutorial Covers

This walk-through is for people who have an old FLV (Flash Video) clip — a downloaded web video, a screen recording, or a file pulled off a long-dead Flash site — and need it inside the AVCHD structure that Sony and Panasonic camcorders, AVCHD discs, and Blu-ray authoring tools expect. By the end you'll have an .mts stream with H.264 video and AC-3 audio, plus a clear-eyed understanding of why upscaling a small FLV into HD AVCHD won't magically add detail.

How to Convert FLV to AVCHD

1. Upload Your FLV File: Drag and drop or click "+ Add Files" to select one or more FLV files. Batch is supported — queue several clips and convert them in one pass.
2. Pick a Quality Preset: AVCHD locks video to H.264 (AVC) and audio to AC-3 (Dolby Digital) automatically. Leave "Very High (Recommended)" for the canonical ~24 Mbit/s AVCHD 1.0 look, or switch the Compression mode to Constant Bitrate, Variable Bitrate, Constant Quality (CRF), or Specific file size to hit a target.
3. Set Resolution and Trim (Optional): Keep original, pick a Preset Resolution (1280×720 and 1920×1080 are the canonical AVCHD modes), or enter a custom Width × Height. Use Trim → Time Range with a start time and duration in HH:MM:SS.sss to cut a single segment.
4. Convert and Download: Click "Convert". Files are uploaded over an encrypted connection, processed on our servers, and deleted automatically a few hours after conversion — no sign-up, no watermark, never shared.

Walk-through: Choosing Bitrate and Resolution for a Low-Res FLV

The honest catch with FLV → AVCHD: most FLV files are modest web-resolution video (often 320×240, 480×360, or at best 1280×720), encoded with Sorenson Spark or VP6 — sometimes H.264 in later files. AVCHD's entire purpose is HD, so its spec assumes 720p or 1080p source. You can fit a small FLV into AVCHD, but upscaling a 480p clip to 1080p only stretches the existing pixels — it adds container compatibility, not real detail. This is a lossy source re-encoded to a lossy target, so there is no quality to "regain."

• If your FLV is already 720p or 1080p: keep the resolution at original (or pick the matching Preset Resolution) and leave the preset at "Very High". The encoder re-encodes to H.264 once and you keep the source detail.
• If your FLV is small (480p or below) and the camcorder/disc demands HD: pick 1280×720 rather than 1920×1080. Upscaling to 720p is gentler and the file stays smaller; jumping straight to 1080p just inflates the bitrate without sharpening anything.
• If you only need a clean stream, not maximum size: drop the preset to "High" or "Medium" — a small upscaled FLV does not benefit from a 24 Mbit/s ceiling, and a lower bitrate keeps the .mts manageable.
• Audio: FLV usually carries MP3, AAC, or ADPCM audio. AVCHD requires AC-3, so the audio track is always re-encoded — expect a one-time, generally inaudible transcode rather than a copy.

Common Errors and How to Fix Them

• "My converted file looks soft / blocky at 1080p" — You upscaled a low-resolution FLV. Re-run at 1280×720 or at the FLV's native resolution; the source simply doesn't contain 1080p detail to recover.
• "The camcorder or Blu-ray player won't see the file" — A lone .mts is just the stream, not a finished AVCHD disc. It needs the surrounding BDMV/STREAM/ folder structure built by an authoring tool (see "When This Doesn't Work" below).
• "Audio is out of sync or silent" — Some old FLV files have variable frame rate or broken audio timestamps from streaming. Try trimming to the segment you need, which forces a clean re-encode of both tracks.
• "File is too large to share after conversion" — AVCHD at high bitrate inflates small sources. Lower the preset, or for general sharing convert to FLV → MP4 instead — MP4 plays nearly everywhere and stays compact.
• "The output won't import into my editor" — A few legacy NLEs want a specific extension. If your tool expects raw camcorder files, output FLV → MTS for the bare .mts.

When This Doesn't Work

AVCHD is a rigid spec: strict resolution tiers (720p / 1080i / 1080p), defined H.264 levels, and a 24 Mbit/s (AVCHD 1.0) or 28 Mbit/s (AVCHD 2.0 progressive) bitrate ceiling. A non-conforming FLV is constrained to fit, which is why some clips are downscaled or capped. Just as important, the converter produces the H.264 + AC-3 stream — it does not burn a playable disc. To make an AVCHD disc that a standalone Blu-ray player or PS4/PS5 will mount, drop the converted .mts into authoring software (multiAVCHD, tsMuxeR, ImgBurn with an AVCHD template, or the built-in tools in Vegas / EDIUS), which generates the BDMV/ index files around your stream. Note that the FLV container still opens fine in VLC and ffmpeg even though Adobe Flash Player itself reached end of life on December 31, 2020 — so if you only need playback, you may not need AVCHD at all. If you want a future-proof, universally playable file instead of a camcorder/disc workflow, FLV → MP4 is almost always the better target.

Frequently Asked Questions

Will converting a low-resolution FLV to AVCHD make it HD?

No. Upscaling a small FLV (say 480×360) to a 1080p AVCHD frame stretches the existing pixels to fill the larger raster — it does not invent detail. AVCHD is an HD-targeted format, so the output is technically HD-resolution, but the picture quality is still bounded by the original FLV. For a clean result, set the resolution to the FLV's native size or step up only to 720p rather than forcing 1080p.

Is the converted .mts file a finished AVCHD disc?

No. The converter outputs the AVCHD stream — H.264 video plus AC-3 audio in an MPEG-2 transport stream (.mts / .m2ts). A playable AVCHD disc also needs the BDMV/ folder structure (STREAM/, PLAYLIST/, and index files), which is generated by disc-authoring software such as multiAVCHD, tsMuxeR, or ImgBurn with an AVCHD template. Import the converted .mts into one of those tools to build the full disc layout.

Why does my FLV audio get re-encoded when I convert to AVCHD?

Because FLV and AVCHD use different audio codecs. FLV typically carries MP3, AAC, or ADPCM audio, while AVCHD requires AC-3 (Dolby Digital) or LPCM. There is no way to keep the original MP3/AAC track inside an AVCHD-compliant stream, so the audio is always re-encoded to AC-3. In our testing, a 480p FLV with an MP3 track converted to AVCHD with the audio transcoded to AC-3 and no audible difference at normal listening levels.

What video and audio codecs does the AVCHD output use?

H.264/AVC video and AC-3 (Dolby Digital) audio — the standard AVCHD codec pair, matching what Sony and Panasonic camcorders record. Both are selected automatically when you choose AVCHD as the output. This is identical to every other → AVCHD conversion on xconvert, because the AVCHD spec mandates that codec pair regardless of the source format.

Will the converted file play on my Sony or Panasonic camcorder?

If the camcorder supports AVCHD ingest (most Sony Handycam, HDR-CX/PJ, FX, and Panasonic HC-V / HC-X models do), the stream is the right format — but you usually need to place it inside the PRIVATE/AVCHD/BDMV/STREAM/ folder on the SD card so the camera's index recognizes it. AVCHD's strict bitrate and level rules also mean a non-conforming FLV is constrained to fit the playback hardware, so very high-bitrate or odd-resolution sources are adjusted automatically.

Should I just convert my FLV to MP4 instead?

For nearly everything except a camcorder or AVCHD-disc workflow, yes. MP4 plays on phones, browsers, smart TVs, and editors with no folder structure or disc authoring, and it keeps any resolution without AVCHD's 1080p ceiling — use FLV → MP4. Pick AVCHD only when a specific device or authoring tool genuinely requires the .mts stream and BDMV layout. To go the other direction — pulling AVCHD footage back into a Flash-era container — see AVCHD → FLV.

How long do you keep my uploaded FLV and the converted file?

Files are uploaded over an encrypted connection, processed on our servers, and deleted automatically a few hours after conversion. We never share or publish your files, there's no watermark, and no sign-up is required.