BytePlus Seed TTS 2.0 vs TTS-1 HD
Which one, when — curated verdict, not a benchmark table
On the facts given these two are interchangeable: seed-tts-2.0 and tts-1-hd both take text in and return audio, both carry the speech capability, both cap out at a 4096-token context, and both bill input at $30 per million tokens. Since the rate cards and units match exactly, there is no cost or context argument either way — choose on vendor preference, voice output that suits your product, or whichever provider you are already integrated with. Run a short sample of your own script through each and keep the one that sounds right.
Pricing
| BytePlus Seed TTS 2.0 | TTS-1 HD | Δ | |
|---|---|---|---|
| Per 1M characters | $30 | $30 | = |
Rates from the live catalog at build time; each model page carries the current card.
Where they sit — price per 1M characters across all 7 text-to-speech models on this billing unit (log scale)
Capabilities
| BytePlus Seed TTS 2.0 | TTS-1 HD | |
|---|---|---|
| Streaming | yes | yes |
| SSML | unsupported | undocumented |
| Billing unit | character | character |
Specs
| BytePlus Seed TTS 2.0 | TTS-1 HD | |
|---|---|---|
| Input modalities | text | text |
| Output modalities | audio | audio |
| Request limit | — | 4096 characters |
| Voices | TTS 2.0 voices carry *_uranus_bigtts speaker IDs and are listed by scenario (General, Entertainment, Education, Dubbing, AudioBook, RolePlay, CustomerService) on the Voice List page per-voice emotion via audio_params.emotion with emotion_scale 1 to 5 (default 4), speech_rate and loudness_rate in [-50, 100], and post_process.pitch in [-12, 12]. | alloy, ash, coral, echo, fable, onyx, nova, sage and shimmer, a smaller set than the full 13-voice TTS list, and voices are currently optimized for English. |
| Languages | English, Chinese, Japanese, German, French, Mexican Spanish, Indonesian Bahasa, Brazilian Portuguese, Italian and Korean | Generally follows the Whisper model’s language support: Afrikaans, Arabic, Armenian, Azerbaijani, Belarusian, Bosnian, Bulgarian, Catalan, Chinese, Croatian, Czech, Danish, Dutch, English, Estonian, Finnish, French, Galician, German, Greek, Hebrew, Hindi, Hungarian, Icelandic, Indonesian, Italian, Japanese, Kannada, Kazakh, Korean, Latvian, Lithuanian, Macedonian, Malay, Marathi, Maori, Nepali, Norwegian, Persian, Polish, Portuguese, Romanian, Russian, Serbian, Slovak, Slovenian, Spanish, Swahili, Swedish, Tagalog, Tamil, Thai, Turkish, Ukrainian, Urdu, Vietnamese and Welsh, despite voices being optimized for English |
| Voice control | context_texts and section_id are TTS 2.0 only: a plain-language instruction steers rate, emotion, volume and style (only the first list value takes effect, and its text is not billed), and section_id links up to 30 rounds or 10 minutes of earlier synthesis as historical context. | none |
| Limits | Integration via uni-directional streaming HTTP, uni- or bi-directional streaming WebSocket and online SDK sampling rate 24K/16K/8K on the uni-directional streaming and non-streaming interfaces, 48K/24K/16K/8K on the bi-directional interface output PCM, OGG_OPUS or MP3 (WAV is accepted but returns multiple headers when streaming) SSML is not supported | Speech generation endpoint (v1/audio/speech) only, with Chat Completions, Responses, Realtime, Batch and Fine-tuning all listed as not supported input text is capped at 4096 characters output mp3 (default), opus, aac, flac, wav or pcm (raw 24 kHz 16-bit signed little-endian samples) realtime playback via chunked transfer encoding |
Specs are transcribed from each vendor’s documentation; a row a vendor does not publish is left out rather than inferred. Full sources: BytePlus Seed TTS 2.0 · TTS-1 HD
Switch between them with one line
Both ids are in every tab below — the highlighted pair of lines is the only edit. Same endpoint, same key, same request shape.
from openai import OpenAI
client = OpenAI(
base_url="https://synthorai.io/v1",
api_key="sk-syn-...",
)
resp = client.audio.transcriptions.create(
model="seed-tts-2.0",
# model="tts-1-hd", # uncomment this line, comment the one above
file=open("meeting.mp3", "rb"),
language="en",
)
print(resp.text)import OpenAI from "openai";
import fs from "node:fs";
const client = new OpenAI({
baseURL: "https://synthorai.io/v1",
apiKey: "sk-syn-...",
});
const resp = await client.audio.transcriptions.create({
model: "seed-tts-2.0",
// model: "tts-1-hd", // uncomment this line, comment the one above
file: fs.createReadStream("meeting.mp3"),
});
console.log(resp.text);curl https://synthorai.io/v1/audio/transcriptions \
-H "Authorization: Bearer sk-syn-..." \
-F model="seed-tts-2.0" \
# -F model="tts-1-hd" \ # uncomment this line, comment the one above
-F file=@meeting.mp3package main
import (
"context"
"fmt"
"os"
"github.com/openai/openai-go/v3"
"github.com/openai/openai-go/v3/option"
)
func main() {
client := openai.NewClient(
option.WithBaseURL("https://synthorai.io/v1"),
option.WithAPIKey("sk-syn-..."),
)
f, _ := os.Open("meeting.mp3")
resp, _ := client.Audio.Transcriptions.New(context.TODO(), openai.AudioTranscriptionNewParams{
Model: "seed-tts-2.0",
// Model: "tts-1-hd", // uncomment this line, comment the one above
File: f,
})
fmt.Println(resp.Text)
}import com.openai.client.OpenAIClient;
import com.openai.client.okhttp.OpenAIOkHttpClient;
import com.openai.models.audio.transcriptions.*;
import java.nio.file.Paths;
OpenAIClient client = OpenAIOkHttpClient.builder()
.baseUrl("https://synthorai.io/v1")
.apiKey("sk-syn-...")
.build();
Transcription resp = client.audio().transcriptions().create(
TranscriptionCreateParams.builder()
.model("seed-tts-2.0")
// .model("tts-1-hd") // uncomment this line, comment the one above
.file(Paths.get("meeting.mp3"))
.build()).asTranscription();
System.out.println(resp.text());FAQ
Which is cheaper, BytePlus Seed TTS 2.0 or TTS-1 HD?
They list the same per 1m characters ($30), so price does not decide this one — see the specs and capabilities below.
Can I A/B test BytePlus Seed TTS 2.0 against TTS-1 HD without two integrations?
Yes. Both are served through the same OpenAI-compatible endpoint with one API key — switching is a one-line model-string change, so you can route a fraction of traffic to each and compare bills directly.
How is text-to-speech billed?
Per character of input text, with a per-request character ceiling shown in the spec table. Long scripts must be chunked across requests on either model.