Merge branch 'fix/qobuz-mobile-fallback-eof'

internal/app/app.go

@@ -91,6 +91,10 @@ type videoDownloadableProvider interface {
 	GetVideoDownloadable(ctx context.Context, videoID string) (*provider.Downloadable, error)
 }
 
+type trackFallbackDownloader interface {
+	DownloadTrackFallback(ctx context.Context, trackID string, quality int, outputPath string) error
+}
+
 func New(cfg *config.Config) (*Main, error) {
 	var db store.Database
 	if cfg.Session.Database.DownloadsEnabled || cfg.Session.Database.FailedDownloadsEnabled {
@@ -885,11 +889,21 @@ func (m *Main) ripTrack(ctx context.Context, p provider.Client, source, id, fall
 	if err = downloadOnce(); err != nil {
 		m.logf("retry: %s (%v)\n", filepath.Base(outPath), err)
 		if err = downloadOnce(); err != nil {
+			if fallbackProvider, ok := p.(trackFallbackDownloader); ok {
+				m.logf("fallback: %s via provider backup flow\n", filepath.Base(outPath))
+				if fbErr := fallbackProvider.DownloadTrackFallback(ctx, id, m.qualityForSource(source), outPath); fbErr == nil {
+					goto downloaded
+				} else {
+					m.logf("fallback failed: %s (%v)\n", filepath.Base(outPath), fbErr)
+				}
+			}
 			_ = m.Store.MarkFailed(ctx, source, "track", id)
 			return fmt.Errorf("id=%s title=%q download: %w", id, title, err)
 		}
 	}
 
+downloaded:
+
 	embedCoverPath := opts.albumEmbedCover
 	if opts.forPlaylist {
 		parent := opts.albumFolder

internal/download/downloader.go

@@ -129,6 +129,11 @@ func (d *Downloader) FileDeezerEncrypted(ctx context.Context, sourceURL, outputP
 			)
 			defer bar.SetTotal(-1, true)
 		}
+		defer func() {
+			if !success && bar != nil {
+				bar.Abort(true)
+			}
+		}()
 	}
 
 	block, err := blowfish.NewCipher(deriveDeezerBlowfishKey(trackID))
@@ -249,6 +254,11 @@ func (d *Downloader) file(ctx context.Context, sourceURL, outputPath string, all
 			)
 			defer bar.SetTotal(-1, true)
 		}
+		defer func() {
+			if !success && bar != nil {
+				bar.Abort(true)
+			}
+		}()
 		buf := make([]byte, downloadBufferSize)
 		totalWritten := int64(0)
 		for {

internal/provider/qobuz/client.go

@@ -1,20 +1,28 @@
 package qobuz
 
 import (
+	"bytes"
 	"context"
+	"crypto/aes"
+	"crypto/cipher"
 	"crypto/md5"
+	"crypto/sha256"
 	"encoding/base64"
 	"encoding/hex"
 	"encoding/json"
 	"errors"
 	"fmt"
+	"hash"
 	"io"
 	"net/http"
 	"net/url"
+	"os"
+	"path/filepath"
 	"regexp"
 	"sort"
 	"strconv"
 	"strings"
+	"sync"
 	"time"
 
 	"streamrip-go/internal/config"
@@ -22,10 +30,28 @@ import (
 	"streamrip-go/internal/netutil"
 	"streamrip-go/internal/provider"
 	"streamrip-go/internal/ratelimit"
+
+	"github.com/vbauerster/mpb/v8"
+	"github.com/vbauerster/mpb/v8/decor"
+	"golang.org/x/crypto/hkdf"
 )
 
 const baseURL = "https://www.qobuz.com/api.json/0.2"
 
+const (
+	mobileAppID        = "312369995"
+	mobileAppSecret    = "e79f8b9be485692b0e5f9dd895826368"
+	mobileUserAgent    = "Dalvik/2.1.0 (Linux; U; Android 9; Nexus 6P Build/PQ3A.190801.002) QobuzMobileAndroid/9.7.0.3-b26022717"
+	mobileAppVersion   = "9.7.0.3"
+	mobileSessionProf  = "qbz-1"
+	mobileSegmentTries = 3
+)
+
+var qobuzUUIDBytes = []byte{
+	0x3b, 0x42, 0x12, 0x92, 0x56, 0xf3, 0x5f, 0x75,
+	0x92, 0x36, 0x63, 0xb6, 0x9a, 0x1f, 0x52, 0xb2,
+}
+
 var (
 	errMissingCredentials = errors.New("missing qobuz credentials")
 	errNotLoggedIn        = errors.New("qobuz client not logged in")
@@ -40,6 +66,23 @@ type Client struct {
 	loggedIn bool
 	secret   string
 	uat      string
+
+	mobileMu          sync.Mutex
+	mobileAccessToken string
+	mobileSessionID   string
+	mobileSessionInfo string
+	mobileKEK         []byte
+}
+
+type mobileFileURL struct {
+	URL         string  `json:"url"`
+	URLTemplate string  `json:"url_template"`
+	NSegments   int     `json:"n_segments"`
+	FormatID    int     `json:"format_id"`
+	MimeType    string  `json:"mime_type"`
+	Sampling    float64 `json:"sampling_rate"`
+	BitDepth    int     `json:"bits_depth"`
+	Key         string  `json:"key"`
 }
 
 func New(cfg *config.Config) *Client {
@@ -399,6 +442,122 @@ func (c *Client) Close() error {
 	return nil
 }
 
+func (c *Client) DownloadTrackFallback(ctx context.Context, trackID string, quality int, outputPath string) error {
+	q := &c.cfg.Session.Qobuz
+	if strings.TrimSpace(q.EmailOrUserID) == "" || strings.TrimSpace(q.PasswordOrToken) == "" || q.UseAuthToken {
+		return errors.New("qobuz mobile fallback requires email/password credentials")
+	}
+	if quality < 1 || quality > 4 {
+		quality = q.Quality
+	}
+	formatID := qualityMap(quality)
+
+	if err := c.ensureMobileSession(ctx); err != nil {
+		return err
+	}
+	fileURL, err := c.mobileGetFileURL(ctx, trackID, formatID)
+	if err != nil {
+		return err
+	}
+
+	if err = os.MkdirAll(filepath.Dir(outputPath), 0o755); err != nil {
+		return err
+	}
+	out, err := os.Create(outputPath)
+	if err != nil {
+		return err
+	}
+	success := false
+	defer func() {
+		_ = out.Close()
+		if !success {
+			_ = os.Remove(outputPath)
+		}
+	}()
+
+	progress := mpb.New(mpb.WithWidth(40), mpb.WithOutput(os.Stderr))
+	defer progress.Wait()
+	desc := shortenName(filepath.Base(outputPath), 54)
+	bar := progress.AddSpinner(
+		0,
+		mpb.PrependDecorators(
+			decor.Name(desc+" ", decor.WC{W: 56, C: decor.DSyncWidth | decor.DindentRight}),
+		),
+		mpb.AppendDecorators(
+			decor.CurrentKibiByte("% .1f", decor.WCSyncWidthR),
+			decor.Name(" | ", decor.WCSyncWidth),
+			decor.Elapsed(decor.ET_STYLE_GO, decor.WCSyncWidthR),
+		),
+		mpb.BarRemoveOnComplete(),
+	)
+	defer func() {
+		if !success {
+			bar.Abort(true)
+		}
+		bar.SetTotal(-1, true)
+	}()
+
+	if strings.TrimSpace(fileURL.URL) != "" && fileURL.NSegments == 0 {
+		err = c.mobileCopyURLToWriter(ctx, strings.TrimSpace(fileURL.URL), out, bar)
+		if err != nil {
+			return err
+		}
+		success = true
+		return nil
+	}
+	if strings.TrimSpace(fileURL.URLTemplate) == "" {
+		return errors.New("qobuz mobile fallback: no download URL available")
+	}
+
+	var trackKey []byte
+	if strings.TrimSpace(fileURL.Key) != "" {
+		trackKey, err = c.mobileDeriveTrackKey(fileURL.Key)
+		if err != nil {
+			return fmt.Errorf("derive mobile track key: %w", err)
+		}
+	}
+
+	nSegs := fileURL.NSegments
+	if nSegs == 0 {
+		nSegs = 1
+	}
+	initURL := strings.Replace(fileURL.URLTemplate, "$SEGMENT$", "0", 1)
+	initData, err := c.mobileDownloadSegment(ctx, initURL)
+	if err != nil {
+		return fmt.Errorf("download init segment: %w", err)
+	}
+
+	if hdr := extractFLACHeader(initData); hdr != nil {
+		if _, err = out.Write(hdr); err != nil {
+			return err
+		}
+		bar.IncrBy(len(hdr))
+	} else {
+		if _, err = out.Write(initData); err != nil {
+			return err
+		}
+		bar.IncrBy(len(initData))
+	}
+
+	for seg := 1; seg <= nSegs; seg++ {
+		segURL := strings.Replace(fileURL.URLTemplate, "$SEGMENT$", strconv.Itoa(seg), 1)
+		data, dlErr := c.mobileDownloadSegment(ctx, segURL)
+		if dlErr != nil {
+			return fmt.Errorf("download segment %d: %w", seg, dlErr)
+		}
+		frames := extractFrames(data, trackKey)
+		if _, err = out.Write(frames); err != nil {
+			return err
+		}
+		bar.IncrBy(len(frames))
+	}
+	if err = out.Sync(); err != nil {
+		return err
+	}
+	success = true
+	return nil
+}
+
 func (c *Client) getPlaylist(ctx context.Context, playlistID string) (map[string]any, error) {
 	pageLimit := 500
 	params := url.Values{}
@@ -820,3 +979,460 @@ func sortedKeys(m map[string][]string) []string {
 	sort.Strings(keys)
 	return keys
 }
+
+func (c *Client) ensureMobileSession(ctx context.Context) error {
+	c.mobileMu.Lock()
+	defer c.mobileMu.Unlock()
+	if c.mobileAccessToken != "" && c.mobileSessionID != "" && c.mobileSessionInfo != "" {
+		return nil
+	}
+	q := &c.cfg.Session.Qobuz
+	if err := c.mobileLogin(ctx, q.EmailOrUserID, q.PasswordOrToken); err != nil {
+		return err
+	}
+	if err := c.mobileStartSession(ctx); err != nil {
+		c.mobileAccessToken = ""
+		return err
+	}
+	return nil
+}
+
+func (c *Client) mobileLogin(ctx context.Context, username, password string) error {
+	ts := time.Now().Unix()
+	params := url.Values{}
+	params.Set("app_id", mobileAppID)
+	params.Set("username", username)
+	params.Set("password", password)
+	params.Set("request_ts", strconv.FormatInt(ts, 10))
+	params.Set("request_sig", mobileSignRequest("oauth2/login", []kv{{"password", password}, {"username", username}}, ts))
+
+	reqURL := baseURL + "/oauth2/login?" + params.Encode()
+	req, err := http.NewRequestWithContext(ctx, http.MethodGet, reqURL, nil)
+	if err != nil {
+		return err
+	}
+	c.setMobileHeaders(req)
+	resp, err := c.http.Do(req)
+	if err != nil {
+		return fmt.Errorf("mobile login request failed: %w", err)
+	}
+	defer func() { _ = resp.Body.Close() }()
+	body, err := io.ReadAll(resp.Body)
+	if err != nil {
+		return err
+	}
+	if resp.StatusCode != http.StatusOK {
+		return fmt.Errorf("mobile login failed: status=%d body=%s", resp.StatusCode, string(body))
+	}
+	var parsed struct {
+		OAuth2 struct {
+			AccessToken string `json:"access_token"`
+		} `json:"oauth2"`
+	}
+	if err = json.Unmarshal(body, &parsed); err != nil {
+		return fmt.Errorf("mobile login parse failed: %w", err)
+	}
+	if strings.TrimSpace(parsed.OAuth2.AccessToken) == "" {
+		return errors.New("mobile login returned empty token")
+	}
+	c.mobileAccessToken = strings.TrimSpace(parsed.OAuth2.AccessToken)
+	return nil
+}
+
+func (c *Client) mobileStartSession(ctx context.Context) error {
+	ts := time.Now().Unix()
+	params := url.Values{}
+	params.Set("app_id", mobileAppID)
+	params.Set("request_ts", strconv.FormatInt(ts, 10))
+	params.Set("request_sig", mobileSignRequest("session/start", []kv{{"profile", mobileSessionProf}}, ts))
+
+	reqURL := baseURL + "/session/start?" + params.Encode()
+	form := url.Values{}
+	form.Set("profile", mobileSessionProf)
+	req, err := http.NewRequestWithContext(ctx, http.MethodPost, reqURL, strings.NewReader(form.Encode()))
+	if err != nil {
+		return err
+	}
+	req.Header.Set("Content-Type", "application/x-www-form-urlencoded")
+	c.setMobileHeaders(req)
+	resp, err := c.http.Do(req)
+	if err != nil {
+		return fmt.Errorf("mobile session request failed: %w", err)
+	}
+	defer func() { _ = resp.Body.Close() }()
+	body, err := io.ReadAll(resp.Body)
+	if err != nil {
+		return err
+	}
+	if resp.StatusCode != http.StatusOK {
+		return fmt.Errorf("mobile session start failed: status=%d body=%s", resp.StatusCode, string(body))
+	}
+	var parsed struct {
+		SessionID string `json:"session_id"`
+		Infos     string `json:"infos"`
+	}
+	if err = json.Unmarshal(body, &parsed); err != nil {
+		return fmt.Errorf("mobile session parse failed: %w", err)
+	}
+	if strings.TrimSpace(parsed.SessionID) == "" || strings.TrimSpace(parsed.Infos) == "" {
+		return errors.New("mobile session start returned incomplete session data")
+	}
+	c.mobileSessionID = strings.TrimSpace(parsed.SessionID)
+	c.mobileSessionInfo = strings.TrimSpace(parsed.Infos)
+	c.mobileKEK = nil
+	return nil
+}
+
+func (c *Client) mobileGetFileURL(ctx context.Context, trackID string, formatID int) (*mobileFileURL, error) {
+	ts := time.Now().Unix()
+	params := url.Values{}
+	params.Set("app_id", mobileAppID)
+	params.Set("track_id", trackID)
+	params.Set("format_id", strconv.Itoa(formatID))
+	params.Set("intent", "stream")
+	params.Set("request_ts", strconv.FormatInt(ts, 10))
+	params.Set("request_sig", mobileSignRequest("file/url", []kv{{"format_id", strconv.Itoa(formatID)}, {"intent", "stream"}, {"track_id", trackID}}, ts))
+	reqURL := baseURL + "/file/url?" + params.Encode()
+	req, err := http.NewRequestWithContext(ctx, http.MethodGet, reqURL, nil)
+	if err != nil {
+		return nil, err
+	}
+	c.setMobileHeaders(req)
+	resp, err := c.http.Do(req)
+	if err != nil {
+		return nil, err
+	}
+	defer func() { _ = resp.Body.Close() }()
+	body, err := io.ReadAll(resp.Body)
+	if err != nil {
+		return nil, err
+	}
+	if resp.StatusCode != http.StatusOK {
+		return nil, fmt.Errorf("mobile file url failed: status=%d body=%s", resp.StatusCode, string(body))
+	}
+	var parsed mobileFileURL
+	if err = json.Unmarshal(body, &parsed); err != nil {
+		return nil, fmt.Errorf("mobile file url parse failed: %w", err)
+	}
+	return &parsed, nil
+}
+
+func (c *Client) mobileCopyURLToWriter(ctx context.Context, sourceURL string, out io.Writer, bar *mpb.Bar) error {
+	req, err := http.NewRequestWithContext(ctx, http.MethodGet, sourceURL, nil)
+	if err != nil {
+		return err
+	}
+	c.setMobileHeaders(req)
+	resp, err := c.http.Do(req)
+	if err != nil {
+		return err
+	}
+	defer func() { _ = resp.Body.Close() }()
+	if resp.StatusCode != http.StatusOK {
+		return fmt.Errorf("mobile fallback download failed: status=%d", resp.StatusCode)
+	}
+	written, err := io.Copy(out, &countingReader{r: resp.Body, onRead: func(n int) {
+		if bar != nil && n > 0 {
+			bar.IncrBy(n)
+		}
+	}})
+	if err != nil {
+		return err
+	}
+	if resp.ContentLength > 0 && written != resp.ContentLength {
+		return io.ErrUnexpectedEOF
+	}
+	return nil
+}
+
+type countingReader struct {
+	r      io.Reader
+	onRead func(int)
+}
+
+func (c *countingReader) Read(p []byte) (int, error) {
+	n, err := c.r.Read(p)
+	if n > 0 && c.onRead != nil {
+		c.onRead(n)
+	}
+	return n, err
+}
+
+func shortenName(name string, max int) string {
+	if max <= 0 {
+		return name
+	}
+	r := []rune(name)
+	if len(r) <= max {
+		return name
+	}
+	if max <= 3 {
+		return string(r[:max])
+	}
+	return string(r[:max-3]) + "..."
+}
+
+func (c *Client) mobileDownloadSegment(ctx context.Context, sourceURL string) ([]byte, error) {
+	var lastErr error
+	for attempt := 0; attempt < mobileSegmentTries; attempt++ {
+		req, err := http.NewRequestWithContext(ctx, http.MethodGet, sourceURL, nil)
+		if err != nil {
+			return nil, err
+		}
+		c.setMobileHeaders(req)
+		resp, err := c.http.Do(req)
+		if err != nil {
+			lastErr = err
+			time.Sleep(time.Duration(500*(attempt+1)) * time.Millisecond)
+			continue
+		}
+		if resp.StatusCode != http.StatusOK {
+			lastErr = fmt.Errorf("status=%d", resp.StatusCode)
+			_ = resp.Body.Close()
+			time.Sleep(time.Duration(500*(attempt+1)) * time.Millisecond)
+			continue
+		}
+		data, readErr := io.ReadAll(resp.Body)
+		_ = resp.Body.Close()
+		if readErr != nil {
+			lastErr = readErr
+			time.Sleep(time.Duration(500*(attempt+1)) * time.Millisecond)
+			continue
+		}
+		return data, nil
+	}
+	if lastErr == nil {
+		lastErr = errors.New("unknown segment error")
+	}
+	return nil, fmt.Errorf("mobile segment download failed after retries: %w", lastErr)
+}
+
+func (c *Client) setMobileHeaders(req *http.Request) {
+	req.Header.Set("User-Agent", mobileUserAgent)
+	req.Header.Set("X-App-Id", mobileAppID)
+	req.Header.Set("X-App-Version", mobileAppVersion)
+	req.Header.Set("X-Device-Platform", "android")
+	req.Header.Set("X-Device-Model", "Nexus 6P")
+	req.Header.Set("X-Device-Os-Version", "9")
+	if c.mobileAccessToken != "" {
+		req.Header.Set("Authorization", "Bearer "+c.mobileAccessToken)
+	}
+	if c.mobileSessionID != "" {
+		req.Header.Set("X-Session-Id", c.mobileSessionID)
+	}
+}
+
+func mobileSignRequest(endpoint string, params []kv, ts int64) string {
+	method := strings.ReplaceAll(endpoint, "/", "")
+	sortKVs(params)
+	var sb strings.Builder
+	sb.WriteString(method)
+	for _, p := range params {
+		sb.WriteString(p.Key)
+		sb.WriteString(p.Value)
+	}
+	sb.WriteString(strconv.FormatInt(ts, 10))
+	sb.WriteString(mobileAppSecret)
+	h := md5.Sum([]byte(sb.String()))
+	return hex.EncodeToString(h[:])
+}
+
+type kv struct {
+	Key   string
+	Value string
+}
+
+func sortKVs(s []kv) {
+	for i := 0; i < len(s); i++ {
+		for j := i + 1; j < len(s); j++ {
+			if s[j].Key < s[i].Key {
+				s[i], s[j] = s[j], s[i]
+			}
+		}
+	}
+}
+
+func (c *Client) mobileDeriveTrackKey(encryptedKey string) ([]byte, error) {
+	if len(c.mobileKEK) == 16 {
+		return unwrapQobuzTrackKey(encryptedKey, c.mobileKEK)
+	}
+	parts := strings.SplitN(c.mobileSessionInfo, ".", 2)
+	if len(parts) != 2 {
+		return nil, errors.New("invalid mobile session infos format")
+	}
+	salt, err := base64.RawURLEncoding.DecodeString(parts[0])
+	if err != nil {
+		return nil, fmt.Errorf("decode mobile salt: %w", err)
+	}
+	info, err := base64.RawURLEncoding.DecodeString(parts[1])
+	if err != nil {
+		return nil, fmt.Errorf("decode mobile info: %w", err)
+	}
+	reader := hkdf.New(func() hash.Hash { return sha256.New() }, hexDecodeOrNil(mobileAppSecret), salt, info)
+	kek := make([]byte, 16)
+	if _, err = io.ReadFull(reader, kek); err != nil {
+		return nil, fmt.Errorf("mobile hkdf derive failed: %w", err)
+	}
+	c.mobileKEK = kek
+	return unwrapQobuzTrackKey(encryptedKey, kek)
+}
+
+func hexDecodeOrNil(s string) []byte {
+	b, _ := hex.DecodeString(s)
+	return b
+}
+
+func unwrapQobuzTrackKey(encryptedKey string, kek []byte) ([]byte, error) {
+	parts := strings.SplitN(encryptedKey, ".", 3)
+	if len(parts) != 3 || parts[0] != mobileSessionProf {
+		return nil, errors.New("invalid qobuz track key format")
+	}
+	encKey, err := base64.RawURLEncoding.DecodeString(parts[1])
+	if err != nil {
+		return nil, fmt.Errorf("decode encrypted key failed: %w", err)
+	}
+	iv, err := base64.RawURLEncoding.DecodeString(parts[2])
+	if err != nil {
+		return nil, fmt.Errorf("decode key iv failed: %w", err)
+	}
+	block, err := aes.NewCipher(kek)
+	if err != nil {
+		return nil, err
+	}
+	decrypted := make([]byte, len(encKey))
+	mode := cipher.NewCBCDecrypter(block, iv)
+	mode.CryptBlocks(decrypted, encKey)
+	if len(decrypted) < 16 {
+		return nil, errors.New("decrypted key too short")
+	}
+	return decrypted[:16], nil
+}
+
+func extractFLACHeader(data []byte) []byte {
+	blocks := findDFLABlocks(data)
+	if blocks == nil {
+		return nil
+	}
+	out := make([]byte, 4+len(blocks))
+	copy(out, "fLaC")
+	copy(out[4:], blocks)
+	return out
+}
+
+func findDFLABlocks(data []byte) []byte {
+	pos := 0
+	for pos+8 <= len(data) {
+		size := int(uint32(data[pos])<<24 | uint32(data[pos+1])<<16 | uint32(data[pos+2])<<8 | uint32(data[pos+3]))
+		if size < 8 || pos+size > len(data) {
+			break
+		}
+		t := data[pos+4 : pos+8]
+		if string(t) == "dfLa" {
+			body := data[pos+8 : pos+size]
+			if len(body) > 4 {
+				return body[4:]
+			}
+		}
+		var inner []byte
+		switch string(t) {
+		case "moov", "trak", "mdia", "minf", "stbl":
+			inner = data[pos+8 : pos+size]
+		case "stsd":
+			if pos+16 <= pos+size {
+				inner = data[pos+16 : pos+size]
+			}
+		case "fLaC":
+			if pos+36 <= pos+size {
+				inner = data[pos+36 : pos+size]
+			}
+		}
+		if inner != nil {
+			if result := findDFLABlocks(inner); result != nil {
+				return result
+			}
+		}
+		pos += size
+	}
+	return nil
+}
+
+func extractFrames(data []byte, key []byte) []byte {
+	var frames []byte
+	pos := 0
+	for pos+8 <= len(data) {
+		boxSize := int(uint32(data[pos])<<24 | uint32(data[pos+1])<<16 | uint32(data[pos+2])<<8 | uint32(data[pos+3]))
+		if boxSize < 8 || pos+boxSize > len(data) {
+			break
+		}
+		if string(data[pos+4:pos+8]) == "uuid" && boxSize >= 36 {
+			if pos+24 > len(data) {
+				pos += boxSize
+				continue
+			}
+			if bytes.Equal(data[pos+8:pos+24], qobuzUUIDBytes) {
+				f := parseUUIDBox(data, pos, boxSize, key)
+				frames = append(frames, f...)
+			}
+		}
+		pos += boxSize
+	}
+	return frames
+}
+
+func parseUUIDBox(data []byte, boxStart, boxSize int, key []byte) []byte {
+	bodyOff := boxStart + 24
+	if bodyOff+12 > len(data) {
+		return nil
+	}
+	rawOffset := readU32BE(data, bodyOff+4)
+	numSamples := int(readU24BE(data, bodyOff+9))
+	if numSamples == 0 || numSamples > 10000 {
+		return nil
+	}
+	tableOff := bodyOff + 12
+	sampleDataOff := boxStart + int(rawOffset)
+	var frames []byte
+	offset := sampleDataOff
+	for i := 0; i < numSamples; i++ {
+		et := tableOff + i*16
+		if et+16 > len(data) || offset >= len(data) {
+			break
+		}
+		size := readU32BE(data, et)
+		encFlag := data[et+6] != 0 || data[et+7] != 0
+		end := offset + int(size)
+		if end > len(data) {
+			break
+		}
+		if encFlag && len(key) == 16 {
+			iv := make([]byte, 16)
+			copy(iv[:8], data[et+8:et+16])
+			block, err := aes.NewCipher(key)
+			if err != nil {
+				return frames
+			}
+			stream := cipher.NewCTR(block, iv)
+			decrypted := make([]byte, end-offset)
+			stream.XORKeyStream(decrypted, data[offset:end])
+			frames = append(frames, decrypted...)
+		} else {
+			frames = append(frames, data[offset:end]...)
+		}
+		offset = end
+	}
+	return frames
+}
+
+func readU32BE(data []byte, off int) uint32 {
+	if off+4 > len(data) {
+		return 0
+	}
+	return uint32(data[off])<<24 | uint32(data[off+1])<<16 | uint32(data[off+2])<<8 | uint32(data[off+3])
+}
+
+func readU24BE(data []byte, off int) uint32 {
+	if off+3 > len(data) {
+		return 0
+	}
+	return uint32(data[off])<<16 | uint32(data[off+1])<<8 | uint32(data[off+2])
+}